Dewatering machine

ABSTRACT

A dewatering machine including: a dewatering tank, formed in a cylindrical shape with a central axis extending in a direction inclined relative to an up-down direction; a balancing ring coaxially arranged in the dewatering tank, liquid for achieving rotational balance of the dewatering tank is contained in the balancing ring and flows freely; a control part. The control part causes the dewatering tank to rotate at a rotating speed lower than a lowest rotating speed at which the dewatering tank resonates in a dewatering preparation stage of washings, so as to detect a biased position of the washings, causes the dewatering tank to stop rotating immediately before the washings biased in the dewatering tank are positioned at an opposite side of liquid biased downward in the balancing rings to a lower side, relative to the central axis.

TECHNICAL FIELD

The present disclosure relates to a dewatering machine.

BACKGROUND

A washing machine with a dewatering function is disclosed in thefollowing patent literature 1. In the washing machine, as for acylindrical washing tank for containing washings, a central axis of thewashing tank is obliquely arranged relative to a plumb line. Therefore,an upper part of the washing tank is obliquely configured in a manner ofprotruding towards a front side of the washing machine.

EXISTING TECHNICAL LITERATURE Patent Literature

Patent literature 1: Japanese Patent Application Laid-open No.2000-312795

Problems to be Solved by the Disclosure

In a dewatering machine in which a dewatering tank for containingwashings is biased like the washing machine in patent literature 1, thewashings are easy to bias in the dewatering tank. If dewateringoperation is conducted in a state that the washings are biased, thedewatering tank will conduct eccentric rotation, thereby causing avibration. Therefore, in the dewatering machine, it is aimed to inhibitthe eccentric rotation of the dewatering tank early, so as to avoidvibration as much as possible.

SUMMARY

The present disclosure is made on the basis of the background and aimsto provide a washing machine capable of inhibiting eccentric rotation ofa biased dewatering tank early.

Solutions for the Problems

The present disclosure provides a dewatering machine, including: adewatering tank, formed in a cylindrical shape with a central axisextending in a direction inclined relative to an up-down direction, thedewatering tank is configured to contain washings, and rotate around thecentral axis so as to dewater the washings; a balancing ring, formed ina hollow annular shape, the balancing ring is coaxially arranged in thedewatering tank, and liquid for achieving rotational balance of thedewatering tank is contained in the balancing ring and flows freely; anda dewatering preparation unit, configured to cause the dewatering tank,in a dewatering preparation stage for the washings, to rotate at arotating speed lower than a lowest rotating speed at which thedewatering tank resonates, so as to detect a biased position of thewashings in the dewatering tank; and cause the dewatering tank to stoprotating immediately before the washings biased in the dewatering tankare positioned, relative to the central axis, at an opposite side of theliquid biased downward in the balancing ring.

In addition, the present disclosure provides a dewatering machine,including: a dewatering tank, formed in a cylindrical shape with acentral axis extending in a direction inclined relative to an up-downdirection, the dewatering tank is configured to contain washings, androtate around the central axis so as to dewater the washings; anelectric motor, configured to cause the dewatering tank to rotate; aninformation value acquisition unit, configured to, when the electricmotor is in an acceleration state of accelerating to a target rotatingspeed used for formally dewatering the washings, sequentially acquire aninformation value that should be decreased as a rotating speed of theelectric motor increases; a counting unit, configured to add a countvalue with an initial value of zero by 1 once the information valueacquisition unit acquires the information value; a calculation unit,configured to calculate an accumulated value of a difference between theinformation value and a previous information value under a conditionthat the information value is larger than the previous informationvalue; a determination unit, configured to determine that the washingsare biased in the dewatering tank when the accumulated value with thecount value of a specified value reaches a first threshold with thecount value of the specified value; and a stopping unit, configured tocause the dewatering tank to stop rotating when it is determined by thedetermination unit that the washings are biased.

In addition, the dewatering machine according to the present disclosurefurther includes an information correction unit, configured to correctthe information value through moving average before the accumulatedvalue is calculated by the calculation unit.

In addition, the dewatering machine according to the present disclosurefurther includes an execution unit, the execution unit is configured toalternatively execute any of a restarting process and a correctionprocess under a condition that the dewatering tank is stopped rotatingthrough the stopping unit, the restarting process is a process forrestarting to dewater the washings by causing the dewatering tank torotate again, and the correction process is a process for correcting thebiasing of the washings in the dewatering tank; and the execution unitis configured to select to execute the correction process rather thanselecting to execute the restarting process in the following situation:the restarting process has been executed for a specified number, and thedewatering tank is caused to stop rotating by the stopping unit

In addition, the dewatering machine according to the present disclosurefurther includes an acceleration unit, and the acceleration unit causesthe electric motor to accelerate in three stages including a firstacceleration stage, a second acceleration stage and a third accelerationstage. The first acceleration stage refers to an acceleration stage, inwhich the motor accelerates toward the target rotating speed fromstarting rotating until the rotating speed of the motor reaches a firstrotating speed, the first rotating speed is higher than a rotating speedat which the dewatering tank resonates transversely and lower than arotating speed at which the dewatering tank resonates longitudinally.The second acceleration stage is an acceleration stage, in which therotating speed of the motor increases from the first rotating speed to asecond rotating speed higher than the first rotating speed. The thirdacceleration stage is an acceleration stage, in which the rotating speedof the motor increases from the second rotating speed to the targetrotating speed. The first threshold is independently set in the firstacceleration stage, the second acceleration stage and the thirdacceleration stage respectively, and the information value acquisitionunit is configured to acquire the information value in the firstacceleration stage, the second acceleration stage and the thirdacceleration stage respectively, the counting unit causes the countvalue to be added by 1 and calculates the accumulated value, and thedetermination unit determines that the washings are biased in thedewatering tank when the accumulated value reaches the first threshold.

In addition, the dewatering machine according to the present disclosurefurther includes a duty ratio acquisition unit, configured to acquire aduty ratio of voltage applied to the motor at each specified time in thethird acceleration stage; and a transformation unit, configured totransform the duty ratio acquired by the duty ratio acquisition unitinto a specified index value. When the index value reaches a secondthreshold for a corresponding time, the determination unit determinesthat the washings are biased in the dewatering tank.

In addition, the dewatering machine according to the present disclosurefurther includes a threshold modification unit, configured to modify thesecond threshold according to the accumulated value in at least oneacceleration stage of the first acceleration stage, the secondacceleration stage and the third acceleration stage.

In addition, in the present disclosure, when a variation of theaccumulated value reaches a third threshold, the determination unitdetermines that the washings are biased in the dewatering tank.

In addition, the present disclosure provides a dewatering machine,including: a dewatering tank, formed in a cylindrical shape with acentral axis extending in a direction inclined relative to an up-downdirection, the dewatering tank is configured to contain washings, androtate around the central axis so as to dewater the washings; an outertank, configured to contain the dewatering tank; an electric motor,configured to cause the dewatering tank to rotate; a determination unit,configured to determine that the washings are biased in the dewateringtank when an information value, relevant to a rotation state of theelectric motor before a rotating speed of the electric motor reaches atarget rotating speed used for formally dewatering the washings, reachesa threshold; a detection unit, configured to mechanically detecteccentric rotation of the dewatering tank by contacting the outer tankwhen the dewatering tank eccentrically rotates along with biasing of thewashings in the dewatering tank and the outer tank is caused to vibrate;a stopping unit, configured to cause the dewatering tank to stoprotating in one of the following situations: it is determined by thedetermination unit that the washings are biased; the eccentric rotationof the dewatering tank is detected by the detection unit; and athreshold correction unit, configured to correct the threshold in one ofthe following situations: a difference between the information value andthe threshold is above the specified value when the eccentric rotationof the dewatering tank is detected by the detection unit; it isdetermined by the determination unit that the washings are biased beforethe eccentric rotation is detected by the detection unit.

In addition, the present disclosure provides a dewatering machine,including: a dewatering tank, formed in a cylindrical shape with acentral axis extending in a direction inclined relative to an up-downdirection, the dewatering tank is configured to contain washings, androtate around the central axis so as to dewater the washings; an outertank, configured to contain the dewatering tank; an electric motor,configured to cause the dewatering tank to rotate; a determination unit,configured to determine that the washings are biased in the dewateringtank when an information value, relevant to a rotation state of theelectric motor before a rotating speed of the electric motor reaches atarget rotating speed used for formally dewatering the washings, reachesa threshold; a detection unit, configured to mechanically detecteccentric rotation of the dewatering tank by contacting the outer tankwhen the dewatering tank eccentrically rotates along with biasing of thewashings in the dewatering tank and the outer tank is caused to vibrate;a stopping unit, configured to cause the dewatering tank to stoprotating in one of the following situations: it is determined by thedetermination unit that the washings are biased; the eccentric rotationof the dewatering tank is detected by the detection unit; and asuspending unit, configured to suspend an operation performed by thestopping unit for stopping the rotation of the dewatering tank, until adetection number of the detection unit reaches a specified number beforeit is determined by the determination unit that the washings are biased.

Effects of Disclosure

According to the present disclosure, since the dewatering tank of thedewatering machine has a cylindrical shape with a central axis extendingalong a direction inclined relative to an up-down direction, thedewatering tank is arranged obliquely. A hollow annular balancing ringis coaxially arranged on the dewatering tank. Thus, in a static state ofthe dewatering tank, liquid contained in the balancing ring is biaseddownwards in the balancing ring.

In the dewatering tank, washings are assumed to be biased in a rotatingdirection of the dewatering tank in a same position as the liquid biaseddownwards in the balancing ring. In the state, when rotation of thedewatering tank is started to dewater the washings, the dewatering tankeccentrically rotates from the beginning of the rotation.

Therefore, in the dewatering machine, in a dewatering preparation stage,a dewatering preparation unit causes the dewatering tank to rotate at avery low speed lower than a maximum rotating speed at which thedewatering tank resonates, so as to detect a biased position of thewashings in the dewatering tank in a rotating direction. The dewateringpreparation unit causes the dewatering tank to stop rotating accordingto the detected biased position immediately before the washings biasedin the dewatering tank will be positioned at an opposite side of theliquid biased downwards in the balancing ring, relative to the centralaxis.

In addition, since the dewatering tank stops rotating when the washingsbiased in the dewatering tank are positioned at the opposite side of theliquid in the balancing ring relative to the central axis, the washingsfinally may come to a same side of the liquid in the balancing ring dueto no time to stop and inertial rotation of the dewatering tank afterstopping.

Therefore, if the dewatering tank stops rotating immediately before thewashings biased in the dewatering tank will be positioned at theopposite side of the liquid in the balancing ring relative to thecentral axis, the washings biased in the dewatering tank and the liquidbiased downwards in the balancing ring can be maintained in a state ofbeing positioned on approximately opposite sides relative the centralaxis. After such preparation stage, when the dewatering tank rotates todewater, the dewatering tank rotates in a state that the liquid in thebalancing ring and the washings are approximately balanced. Thus,eccentric rotation of the dewatering tank obliquely arranged can beearly inhibited.

According to the present disclosure, the dewatering tank of thedewatering machine has a cylindrical shape having the central axis whichextends along the direction inclined relative to the up-down direction,and is arranged obliquely. In the dewatering machine which uses a motorto rotate the dewatering tank, in a state that the motor is acceleratedto a target rotating speed for formally dewatering the washings,information values which are decreased with the increase of the rotatingspeed of the motor are acquired successively. When the informationvalues are obtained each time, a count value with an initial value ofzero is added by 1.

If the washings in the dewatering tank are biased, an information valueat a certain time becomes larger than a previous information valuesometimes since an information value which shall be decreased ischanged. In this case, an accumulated value of a difference between theinformation value and the previous information value is larger thanzero. If the dewatering tank continues to rotate in a state that thewashings in the dewatering tank are biased, the accumulated valuebecomes larger.

Moreover, when the accumulated value when the count value is thespecified value reaches a first threshold when the count value is thespecified value, it is determined that the washings are biased in thedewatering tank, and the dewatering tank stops rotating. Thus, under acondition that the washings are biased in the obliquely arrangeddewatering tank, eccentric rotation of the dewatering tank may beinhibited early in an acceleration state of the motor.

According to the present disclosure, since an information value used incalculation of the accumulated value is corrected through moving averagebefore calculation of the accumulated value, the information value is ahigh accuracy value of eliminating an error. Thus, the accumulated valuewith high accuracy is calculated according to the corrected informationvalue, and whether the washings are biased is detected through theaccumulated value with high accuracy, so that eccentric rotation of thedewatering tank may be inhibited early.

According to the present disclosure, under a condition that the washingsare biased in the dewatering tank and the dewatering tank stopsrotating, the restarting process or the correction process is executed.The restarting process is a process for restarting to dewater thewashing by enabling the dewatering tank to rotate again, and thecorrection process is a process for correcting washing biasing in thedewatering tank.

Dewatering is started again through the restarting process under acondition that washing biasing is small to an extent without generatingeccentric rotation of the dewatering tank, so that time used by thewhole dewatering process may be shortened as much as possible. Under acondition that washing biasing is large to an extent that eccentricrotation of the dewatering tank is still generated, washing biasing maybe reliably corrected through the correction process.

Under a condition that the restarting process is executed for thespecified number and the dewatering tank stops rotating, washing biasingis large to an extent needing to be corrected. In this case, thecorrection process is quickly executed without spending time on carryingout the restarting process repeatedly and stopping rotation of thedewatering tank, so that biasing may be reliably corrected. Thus,eccentric rotation of the dewatering tank may be inhibited early.

According to the present disclosure, in the first acceleration stage,the second acceleration stage and the third acceleration stage of themotor from starting rotation to reaching the target rotating speed, theaccumulated values are respectively calculated, and when the accumulatedvalues reach the corresponding first thresholds in the firstacceleration stage, the second acceleration stage and the thirdacceleration stage respectively, washing biasing in the dewatering tankmay be determined, so that the dewatering tank stops rotating. Namely,since the biasing of the washings is detected in the first accelerationstage after the motor starts to rotate, eccentric rotation of thedewatering tank may be inhibited early. Furthermore, since the biasingof the washings is detected in three stages according to a sequence ofthe first acceleration stage, the second acceleration stage and thethird acceleration stage, the condition of washing biasing may bereliably detected, and eccentric rotation of the dewatering tank isinhibited as early as possible.

According to the present disclosure, in the third acceleration stage,when the duty ratio acquired at each specified moment is transformedinto a specified index value, and the index value reaches a secondthreshold at a corresponding moment, it is determined that the washingsare biased in the dewatering tank. That is, in the third accelerationstage, since the condition whether the washing is biased in thedewatering tank is double detected by adopting a mode of the informationvalues and the first thresholds and adopting a mode of the duty ratioand the second thresholds, eccentric rotation of the dewatering tank maybe reliably inhibited early.

According to the present disclosure, since the second threshold isproperly changed according to the accumulated value in at least oneacceleration stage of the first acceleration stage, the secondacceleration stage and the third acceleration stage, whether thewashings are biased may be detected with high accuracy through thesecond threshold changed with combination of a situation of thedewatering tank, and eccentric rotation of the dewatering tank isinhibited early.

According to the present disclosure, whether the washings are biased maybe double detected through a mode whether the accumulated value reachesthe first threshold and whether a variation of the accumulated valuereaches the third threshold. In this case, whether the dewatering tankis in a state of large amplitude vibration, eccentric rotation of thedewatering tank may be reliably inhibited early according to thevariation of the accumulated value though the accumulated value may besmall without reaching the first threshold.

According to the present disclosure, the dewatering tank of thedewatering machine is in a cylindrical shape with a central axisextending in the direction inclined relative to the up-down directionand is obliquely arranged. Whether the washings are biased in thedewatering tank is double detected through an electric mode based on arelationship between the information value relative to the rotationstate of the motor and the threshold and a mechanical mode based oncontact between the detection unit and the outer tank.

In the dewatering machine in the shipment stage, due to an inclineddifference of the dewatering tanks among individual dewatering machines,some dewatering machines may have a condition that the threshold is notcorrect. Thus, the threshold is corrected under the following situation:a difference between the information value when the detection unitdetects eccentric rotation of the dewatering tank and a threshold isabove the specified value, or the determination unit determines that thewashings are biased before eccentric rotation is detected by thedetection unit. Thus, in the dewatering process after the threshold iscorrected, in the electric mode, whether the washings are biased isdetected with high accuracy through the corrected threshold, so thateccentric rotation of the dewatering tank is inhibited early.

According to the present disclosure, the dewatering tank of thedewatering machine is in the cylindrical shape with the central axisextending in the direction inclined relative to up-down direction and isobliquely arranged. Whether the washings are biased in the dewateringtank is double detected through the electric mode based on arelationship between the information value relative to the rotationstate of the motor and the threshold and a mechanical mode based oncontact between the detection unit and the outer tank.

It is assumed that vibration of the dewatering tank is not too large,but due to the moving mode of the outer tank, the detection unit easilycontacts the outer tank to generate error detection in the mechanicalmode to cause the dewatering tank to stop rotating. Thus, until thedetection number of the detection unit reach the specified number beforethe determination unit determines that the washings are biased, rotationstopping of the dewatering tank is suspended. Thus, not only thedewatering tank is prevented from stopping rotating due to errordetection of the mechanical mode, but also eccentric rotation of thedewatering tank may be inhibited early.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic longitudinal sectional right side viewillustrating a dewatering machine according to an embodiment of thepresent disclosure.

FIG. 2 is a block diagram illustrating an electric structure of adewatering machine.

FIG. 3 is a sequence diagram illustrating a state of an output signal ofa Hall IC forming a rotating speed reading apparatus for reading arotating speed of a motor.

FIG. 4 is a sequence diagram illustrating a state of a rotating speed ofa motor in a dewatering operation process implemented in a dewateringmachine.

FIG. 5 is a schematic diagram illustrating an interior of a dewateringtank.

FIG. 6 is a sequence diagram illustrating a state of a rotating speed ofa motor at a preparation stage of dewatering operation.

FIG. 7 is a flow chart illustrating a control action at the preparationstage of dewatering operation.

FIG. 8 is a flow chart illustrating a control action in a firstacceleration stage of a motor in a dewatering operation process.

FIG. 9A is a flow chart illustrating a control action related todetection 1 to detection 3 for detecting washings biasing in thedewatering tank in a first acceleration stage to a third accelerationstage of a motor.

FIG. 9B is a flow chart illustrating a control action related todetection 1 to detection 3.

FIG. 10 is a diagram illustrating a relationship between a count value nand a moving average value Cn in combination with detection 1 todetection 3.

FIG. 11 is a diagram illustrating a relationship between a count value nand an accumulated value G in combination with detection 1 to detection3.

FIG. 12 is a flow chart illustrating a control action when a detectionresult is no good (NG).

FIG. 13 is a flow chart illustrating a control action in the secondacceleration stage of the motor.

FIG. 14 is a flow chart illustrating a control action in the thirdacceleration stage of a motor.

FIG. 15 is a flow chart illustrating schemas of the detection 4-1 andthe detection 4-2 for detecting whether there is washings biasing in thedewatering tank in the third acceleration stage.

FIG. 16 is a flow chart illustrating a control action of the detection4-1.

FIG. 17 is a diagram illustrating a relationship between the rotatingspeed and a moving accumulated value Cm in combination with detection4-1 and detection 4-2.

FIG. 18 is a flow chart illustrating a control action of the detection4-2.

FIG. 19 is a flow chart illustrating a first modification of a controlaction of the detection 3 in the third acceleration stage.

FIG. 20 is a schematic diagram illustrating an interior of thedewatering tank in the dewatering operation process.

FIG. 21 is a flow chart illustrating a second modification of a controlaction of detection 3 in the third acceleration stage.

FIG. 22 is a flow chart illustrating a control action of a thirdmodification in the dewatering operation process.

FIG. 23 is a flow chart illustrating a control action of the thirdmodification.

FIG. 24 is a flow chart illustrating a control action of a fourthmodification.

FIG. 25 is a flow chart illustrating a control action of a fifthmodification.

REFERENCE NUMERALS LIST

1: dewatering machine; 3: outer tank; 4: dewatering tank; 6: motor; 17:central axis; 19: balancing ring; 30: control part; 34: counter; 36:safety switch; C_(m): moving accumulated value; C_(n): moving averagevalue; d_(m): duty ratio; D_(n): difference; G: accumulated value; K:inclined direction; n: count value; Q: washings; Z: up-down direction;Z2: lower side.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described in detail byreferring to the drawings below.

FIG. 1 is a schematic longitudinal sectional right side viewillustrating a dewatering machine 1 according to an embodiment of thepresent disclosure. An up-down direction in FIG. 1 is referred to as anup-down direction Z of the dewatering machine 1, and a left-rightdirection in FIG. 1 is referred to as a front-rear direction Y of thedewatering machine 1. Firstly, description is made to summary of thedewatering machine 1. In the up-down direction Z, an upper side isreferred to as an upper side Z1, and a lower side is referred to as alower side Z2. In the front-rear direction Y, a left side in FIG. 1 isreferred to as a front side Y1, and a right side in FIG. 1 is referredto as a rear side Y2.

The dewatering machine 1 includes all apparatuses capable of carryingout a dewatering operation of washings Q. That is, the dewateringmachine 1 not only includes an apparatus with a dewatering function, butalso includes a washing machine with a dewatering function and a washingand drying machine. Description is made in regard to the dewateringmachine 1 by taking the washing machine as an example below.

The dewatering machine 1 includes: a housing 2, an outer tank 3, adewatering tank 4, a rotary wing 5, an electric motor 6, and atransmission mechanism 7.

The housing 2 is made of, such as, metal, and formed in a box shape. Anupper surface 2A of the housing 2 is formed to be inclined relative to ahorizontal direction (HD) in a manner of extending to the upper side Z1toward the rear side Y2. An opening 8 to enable the inside and outsideof the housing 2 to be communicated is formed in the upper surface 2A. Adoor 9 for opening and closing the opening 8 is arranged on the uppersurface 2A. An operation part 10 consisting of a LCD operation panel andthe like is arranged in an area closer the front side Y1 than theopening 8 on the upper surface 2A. A user could select a dewateringcondition freely, or make indications, such as an indication of startingto run, an indication of stopping running, to the dewatering machine 1,by operating the operation part 10.

The outer tank 3 is made of, such as, resin, and formed in a cylindricalshape having a bottom. The outer tank 3 has: a circumferential wall 3A,which is roughly cylindrical and configured along an inclined directionK inclined toward the front side Y1 relative to the up-down direction Z;a bottom wall 3B, configured to block a hollow part of thecircumferential wall 3A from the lower side Z2; and an annular wall 3C,which is annular and protrudes towards a circle center side of thecircumferential wall 3A while covering an edge at a side of the upperside Z1 of the circumferential wall 3A. The inclined direction Kpresents inclination not only relative to the up-down direction Z, butalso relative to the horizontal direction (HD). An entrance 11communicated with the hollow part of the circumferential wall 3A fromthe upper side Z1 is formed inside the annular wall 3C. The entrance 11is opposite to the opening 8 of the housing 2 from the lower side Z2,and the entrance 11 and the opening 8 are in a communicated state. Adoor 12 for opening and closing the entrance 11 is arranged on theannual wall 3C. The bottom wall 3B is formed in a circulate plate shapewhich is orthogonal to the inclined direction K and obliquely extendsrelative to the horizontal direction (HD). A through hole 3D penetratingthrough the bottom wall 3B is formed in a circle center of the bottomwall 3B.

Water can be stored in the outer tank 3. A water feeding pipeline 13connected with a faucet of tap water is connected with the outer tank 3from the upper side Z1, so that the tap water is fed to the outer tank 3through the water feeding pipeline 13. A feeding valve 14 which can beopened and closed to start or stop water feeding is arranged in a midwayof the water feeding pipeline 13. A drainage pipeline 15 is connectedwith the outer tank 3 from the lower side Z2, and the water in the outertank 3 is discharged outside the machine from the drainage pipeline 15.A drainage valve 16 which can be opened and closed to start or stopdrainage is arranged in a midway of the drainage pipeline 15.

The dewatering tank 4 is made of, such as, metal, and has a central axis17 extending along the inclined direction K. The dewatering tank 4 isformed in a cylindrical shape having a bottom smaller than that of theouter tank 3, and can accommodate the washings Q internally. Thedewatering tank 4 has a roughly cylindrical circumferential wall 4Aarranged along the inclined direction K and a bottom wall 4B forblocking a hollow part of the circumferential wall 4A from the lowerside Z2.

An internal circumferential surface of the circumferential wall 4A is aninternal circumferential surface of the dewatering tank 4. An upper endof the internal circumferential surface of the circumferential wall 4Ais an entrance 18 for enabling the hollow part of the circumferentialwall 4A to expose to the upper side Z1. The entrance 18 is opposite tothe entrance 11 of the outer tank 3 from the lower side Z2, and theentrance 18 and the entrance 11 are in a communicated state. Theentrances 11 and 18 are opened and closed through the door 12 together.A user of the dewatering machine 1 takes the washings Q in and out ofthe dewatering tank 4 through the opened opening 8 and the entrances 11and 18.

The dewatering tank 4 is coaxially accommodated in the outer tank 3, andis obliquely arranged relative to the up-down direction Z and thehorizontal direction HD. The dewatering tank 4 accommodated in the outertank 3 can rotate around the central axis 17. A plurality of throughholes which are not shown are formed in the circumferential wall 4A andthe bottom wall 4B of the dewatering tank 4, and the water in the outertank 3 can flow between the outer tank 3 and the dewatering tank 4through the through holes. Therefore, a water level in the outer tank 3is consistent with a water level in the dewatering tank 4.

A balancing ring 19 formed in a hollow annular shape is coaxiallyarranged at the upper end of the circumferential wall 4A, and is usedfor reducing vibration of the dewatering tank 4 when the dewatering tank4 rotates so as to obtain rotational balance of the dewatering tank 4.Liquids for obtaining the rotational balance of the dewatering tank 4,such as saline water, are accommodated in an annular cavity 19A in thebalancing ring 19 in a free flow manner.

The bottom wall 4B of the dewatering tank 4 is formed in a circulateplate shape extending with the bottom wall 3B of the outer tank 3 inparallel roughly across the gap in the upper side Z1, and a through hole4C penetrating through the bottom wall 4B is formed at a circle centerof the bottom wall 4B consistent with the central axis 17. A tubularsupporting shaft 20 surrounding the through hole 4C and protruding tothe lower side Z2 along the central axis 17 is arranged on the bottomwall 4B. The supporting shaft 20 is inserted into the through hole 3D onthe bottom wall 3B of the outer tank 3, and a lower end of thesupporting shaft 20 is located in the lower side Z2 of the bottom wall3B.

The rotary wing 5, i.e. so-called impeller, is formed in a discoid shapeby taking the central axis 17 as a circle center, and is concentricallyarranged with the dewatering tank 4 along the bottom wall 4B in thedewatering tank 4. A plurality of blades 5A radially configured arearranged on an upper surface of the rotary ring 5 facing the entrance 18of the dewatering tank 4 from the lower side Z2. A rotating shaft 21extending toward the lower side Z2 from a circle center of the rotarywing 5 along the central axis 17 is arranged on the rotary wing 5. Therotating shaft 21 is inserted into a hollow part of the supporting shaft20, and a lower end of the rotating shaft 21 is located in the lowerside Z2 of the bottom wall 3B of the outer tank 3.

In the present embodiment, the motor 6 is realized through a variablefrequency motor. The motor 6 is arranged in the lower side Z2 of theouter tank 3 in the housing 2, and is provided with an output shaft 22rotating by centering the central axis 17. The transmission mechanism 7is located between the lower ends of both the supporting shaft 20 andthe rotating shaft 21, and an upper end of the output shaft 22. Thetransmission mechanism 7 selectively transmits a driving force outputtedby the motor 6 from the output shaft 22 to one or both of the supportingshaft 20 and the rotating shaft 21. A widely known transmissionmechanism can be taken as the transmission mechanism 7.

The dewatering tank 4 and the rotary wing 5 rotates around the centralaxis 17 when the driving force from the motor 6 is transmitted to thesupporting shaft 20 and the rotating shaft 21. The washings Q in thedewatering tank 4 are stirred through the rotating dewatering tank 4 andthe blades 5A of the rotary wing 5 during a washing operation and arinsing operation. In addition, a centrifugal force acts on the washingsQ in the dewatering tank 4 through high-speed integrated rotation of thedewatering tank 4 and the rotary wing 5 during a dewatering operationafter the rinsing operation. Thus, the washings Q are dewatered. Arotation direction of the dewatering tank 4 and the rotary wing 5 isconsistent with a circumferential direction X of the dewatering tank 4.

FIG. 2 is a block diagram illustrating an electric structure of thedewatering machine 1.

By referring to FIG. 2, the dewatering machine 1 includes: a dewateringpreparation unit, an information value acquisition unit, a countingunit, a calculation unit, a determination unit, a stopping unit, aninformation correction unit, an execution unit, an acceleration unit, aduty ratio acquisition unit, a conversion unit, a threshold changingunit, a threshold correction unit and a control part 30 served as asuspending unit. The control part 30 is configured as a microcomputerincluding: for example, CPU 31; memory 32 such as a ROM, a RAM; a timer33; and as a counter 34 served as the counting unit, and the controlpart 30 is internally placed in the housing 2 (referring to FIG. 1).

The dewatering machine 1 further includes: a water level sensor 35, asafety switch 36 as a detection unit, and a rotating speed readingapparatus 37. The water level sensor 35, the safety switch 36, therotating speed reading apparatus 37, the motor 6, the transmissionmechanism 7, the feeding valve 14, the drainage valve 16 and theoperation part 10 are electrically connected with the control part 30respectively.

The control part 30 switches a transmission target of the driving forceof the motor 6 to one or both of the supporting shaft 20 and therotating shaft 21 by controlling the transmission mechanism 7. Thecontrol part 30 controls opening and closing of the feeding valve 14 andthe drainage valve 16. As mentioned above, when the user selects thedewatering condition and the like of the washings Q by operating theoperating part 10, the control part 30 receives the selection.

The water level sensor 35 is a sensor for detecting the water level ofthe outer tank 3 and the dewatering tank 4, and a detection result ofthe water level sensor 35 is inputted into the control part 30 in realtime.

The safety switch 36 is a switch for detecting a vibration of the outertank caused by an eccentric rotation of the dewatering tank 4 along withbias of the washings Q in the dewatering tank 4, and is arranged at aposition away from the outer tank 3 by a specified interval along thehorizontal direction HD in the housing 2 (referring to FIG. 1). When theouter tank 3 is caused to vibrate along the horizontal direction HDsubstantially due to the eccentric rotation of the dewatering tank 4along with the bias of the washings Q in the dewatering tank 4, theouter tank 3 comes into contact with the safety switch 36 in forward andtransverse directions. Thus, the safety switch 36 is changed into “on”,so as to detect the vibration of the outer tank 3 mechanically, namely,the eccentric rotation of the dewatering tank 4. The detection result ofthe safety switch 36 is inputted into the control part 30 in real time.

The rotating speed reading apparatus 37 is an apparatus for reading arotating speed of the motor 6, and more specifically, is an apparatusfor reading a rotating speed of the output shaft 22 of the motor 6, andconsists of for example a plurality of Hall IC40. The rotating speedread by the rotating speed reading apparatus 37 is inputted into thecontrol part 30 in real time. The control part 30 controls a duty ratioof a voltage applied to the motor 6 according to the inputted rotatingspeed, so that the motor 6 rotates with a desired rotating speed. On theother hand, the control part 30 applies a brake to the rotation of themotor 6 to stop the rotation of the dewatering tank 4 based on a factthat the eccentric rotation of the dewatering tank 4 is detected by thesafety switch 36. The braker herein can cause a control part 30 tocontrol the duty ratio to stop the rotation of the motor 6 urgently, andalso can cause the control part 30 to start a brake device byadditionally arranging the brake device (not shown), thereby stoppingthe rotation of the motor 6 urgently.

For example, the number of Hall IC40 is 3 in the present embodiment. TheHall IC40 are divided into a first Hall IC41, a second Hall IC42 and athird Hall IC43. Herein, the motor 6 has a rotor (not shown) integrallyrotating with the output shaft 22, and magnets in a N-pole and magnetsin a S-pole are arranged alternately in rows in a rotation direction ofthe rotor on an external circumferential surface of the rotor. If agroup consisting of adjacent magnets in the N-pole and magnets in theS-pole are called as a “NS group”, a plurality of NS groups are arrangedalong the rotation direction side by side on the externalcircumferential surface of the rotor. The first Hall IC41, the secondHall IC42, and the third Hall IC43 are arranged along the rotationdirection of the rotor at regular intervals side by side according tosuch sequence. As the rotor rotates, each NS group passes through eachHall IC40 along the rotation direction in sequence. When the NS grouppasses through, each Hall IC40 transmits a pulse P. The rotating speedreading apparatus 37 reads the rotating speed of the motor 6 through asize of an interval of the adjacent pulses P.

FIG. 3 is a sequence diagram illustrating a state of an output signal ofthe Hall IC40 forming the rotating speed reading apparatus 37. In thesequence diagram of FIG. 3, a horizontal axis indicates an elapsed time,and a vertical axis indicates an “on” and “off” state of the outputsignal of each Hall IC. As shown in FIG. 3, there exists a deviationbetween times that the first Hall IC41, the second Hall IC42 and thethird Hall IC43 produce the pulse P. Therefore, when a certain NS grouppasses through each Hall IC40 in sequence, the first Hall IC41, thesecond Hall IC42 and the third Hall IC43 produce the pulses Prespectively according to such sequence.

An “on” state indicating a state in which the pulse P is produced and an“off” state other than the “on” state are presented in a waveform of anoutput signal of each Hall IC40. “Interruption W” is defined asswitching from the “off” state to the “on” state and switching from the“on” state to the “off” state. The interruption W has a time at whichthe pulse P is produced and a time at which the pulse P is disappearedtwice in one pulse P. When the interruption W occurs, the object of suchsituation is to input from the rotating speed reading apparatus 37 tothe control part 30 in real time. It shall be noted that, the times thatthe rotor 1 of the motor 6 produces the interruption W during rotationare different due to number of poles of the motor 6.

As shown in FIG. 3, when there are three Hall IC40 like in the presentembodiment, for example, in a period R of the first Hall IC41 from thetime at which the pulse P1 disappears to a time at which the next pulseP2 is produced and then disappears, the three Hall IC40 produce sixinterruptions W in total. With respect to the entire three Hall IC 40,it is desired that an interval I from some interruption W to the nextinterruption W is always the same in a steady rotation state of themotor 6.

However, the interval I may also be disordered even if the motor 6rotates steadily, due to an installation error of the NS group of themotor 6 and an installation error of each Hall IC40. It shall be notedthat, generally, the interval I is slowly decreased when the motor 6 isin an acceleration state. The interval I can be a value which is thesame as a time unit (such as second), and can also be a summing value ofcounts in each interval I when the counter 34 (referring to FIG. 2)counts once according to a fixed period.

Then, description is made to the dewatering operation conducted in thedewatering machine 1.

FIG. 4 is a sequence diagram illustrating a state of a rotating speed ofthe motor 6 in the dewatering operation process. In the sequence diagramof FIG. 4, a horizontal axis indicates the elapsed time, and a verticalaxis indicates a rotating speed of the motor 6 (unit: rpm). It shall benoted that, the rotating speed of the dewatering tank 4 is the same asthat of the motor 6 during the dewatering operation.

By referring to FIG. 4, at the beginning of the dewatering operation, apreparation stage, i.e., a dewatering preparation interval, of thewashings Q is provided. In the dewatering preparation interval, thecontrol part 30 adjusts a position relationship between the washings Qin the dewatering tank 4 and liquid in the balancing ring 19. After thedewatering preparation interval, the control part 30 starts the rotationof the motor 6, so as to dewater the washings Q.

Specifically, after the dewatering preparation interval, the controlpart 30 causes the motor 6 to rotate steadily at 120 rpm after therotating speed of the motor 6 being increased from 0 rpm to 120 rpm,i.e. a first rotating speed. The first rotating speed is greater than arotating speed (such as 50 rpm˜60 rpm) at which a transverse resonanceoccurred on the dewatering tank 4, and is smaller than a rotating speed(such as 200 rpm˜220 rpm) at which a longitudinal resonance occurred onthe dewatering tank 4. After the motor 6 rotates at 120 rpm steadily,the control part 30 causes the motor 6 to rotate steadily at 240 rpmafter the rotating speed of the motor 6 being increased from 120 rpm to240 rpm, i.e. a second rotating speed. The second rotating speed isslightly greater than the rotating speed at which the longitudinalresonance is occurred. Next, the control part 30 causes the motor 6 torotate steadily at 800 rpm after the rotating speed of the motor 6 beingincreased from 240 rpm to 800 rpm, i.e. a target rotating speed. Thewashings Q in the dewatering tank 4 are formally dewatered through thesteady rotation of the motor 6 at 800 rpm.

In this way, the control part 30 causes the motor 6 to acceleratethrough three stages i.e., a first acceleration stage of enabling themotor 6 to rotate to 120 rpm from the beginning, a second accelerationstage of rotating from 120 rpm to 240 rpm, and a third accelerationstage of rotating from 240 rpm to 800 rpm, so as to reach a target 800rpm. Different from such situation, if the motor 6 is accelerated to 800rpm from 0 rpm uninterruptedly, a drainage state of the drainagepipeline 15 may be deteriorated since a lot of water leaks from thewashings Q, or the drainage pipeline 15 is jammed with foam. However, inthe present embodiment, the motor 6 is accelerated stepwise so that alot of water will not leak from the washings Q at one time. Therefore,such bad condition can be prevented.

When the washings Q in the dewatering tank 4 are in a bias configurationstate of being distributed on the circumferential direction X (referringto FIG. 1) of the dewatering tank 4 unevenly, the washings Q are biasedin the dewatering tank 4. If the dewatering operation is carried out insuch state, the dewatering tank 4 may be substantially shaken due to theeccentric rotation thereof, thereby applying great vibration to thedewatering machine 1, producing noise.

Therefore, the control part 30 detects whether the washings Q in thedewatering tank 4 are biased during the dewatering operation, and stopsthe motor 6 when detecting that the washings Q are biased. The controlpart 30 performs four electric detections, i.e. detection 1, detection2, detection 3 and detection 4, in such detection mode. It shall benoted that, the mechanical detection of the safety switch 36 (referringto FIG. 1) is performed in the whole period of the dewatering operation.It shall be noted that, the term “detection” below refers to an actionof inspecting, and the term “check” refers to an action of finding someresult during the detection.

Detection 1 is performed at the first acceleration stage. Detection 2 isperformed at the second acceleration stage. Detection 3 and detection 4are performed at the third acceleration stage. Specifically, detection 1to detection 3 are performed in the whole period of the correspondingacceleration stages in the first acceleration stage to the thirdacceleration stage, and relative to this, detection 4 is performed in amidway of the third acceleration stage. In this way, the motor 6 isaccelerated in three stages in the dewatering machine 1, therebymonitoring a rotation state of the dewatering tank 4 through detections1-4 while avoiding performing the dewatering slowly at the rotatingspeeds at which the transverse resonance and the longitudinal resonanceoccurred, namely, 120 rpm and 240 rpm. Description is made to thedewatering preparation stage and detections 1-4 in sequence below.

Firstly, description is made to the dewatering preparation stage. FIG. 5is a schematic diagram illustrating an interior of the dewatering tank4. FIG. 5 shows an interior of the dewatering tank 4 viewed along adirection of the central axis 17 of the dewatering tank 4. A frontposition biasing toward the front side Y1 and a deep position biasingtoward the rear side Y2 are presented in the dewatering tank 4. Sincethe central axis 17 is arranged obliquely towards the front side Y1relative to the up-down direction Z, the front position is located at aposition closer to the lower side Z1 than the deep position (referringto FIG. 1). Since the liquid accommodated in the balancing ring 19 isfree of the effect of the centrifugal force generated by the rotation ofthe dewatering tank 4 in a state that the dewatering tank 4 is staticand that the dewatering tank 4 rotates at a very low speed, the liquidaccommodated in the balancing ring 19 is provided at the front positionin the balancing ring 19 due to a self-weight and biased towards thelower side Z2.

In the case that the washings Q are placed in the dewatering tank 4 in amanner of being biased along the circumferential direction X, when thedewatering tank 4 starts to rotate, relative to the central axis 17, thewashings Q are preferably located at the deep position at a sideopposite to the liquid biased to the front position in the lower side Z2in the balancing ring 19. If the washings Q are in such state, theeccentric rotation of the dewatering tank 4 can be inhibited from thebeginning of the rotation since the dewatering tank 4 starts to rotatein a state that the washings Q and the liquid in the balancing ring 19are roughly balanced.

In contrast, it is assumed that, in the dewatering tank 4, the washingsQ are biased in the circumferential direction X of the dewatering tank 4at a position same as the position where the liquid in the balancingring 19 is biased towards the lower side Z2. In the state, when thedewatering tank 4 starts to rotate to dewater the washings Q, thedewatering tank 4 carries out the eccentric rotation when starting torotate.

FIG. 6 is a sequence diagram illustrating a state of the rotating speedof the motor 6 at the preparation stage of dewatering operation. In thesequence diagram of FIG. 6, a horizontal axis indicates the elapsedtime, and a vertical axis indicates the rotating speed of the motor 6(unit: rpm). The dewatering tank 4 rotates steadily at a very low speedat the preparation stage. It shall be noted that, the rotating speed ofthe motor 6 at this time is lower than a minimum rotating speed when aresonance occurred on the dewatering tank 4. The minimum rotating speedis different due to different sizes of the dewatering tank 4, and is arotating speed when the transverse resonance occurred on the dewateringtank 4 in the present embodiment, namely, 50 rpm-60 rpm described above.In this case, for example, the rotating speed of the motor 6 at thepreparation stage is 10 rpm-30 rpm, preferably 20 rpm.

If the dewatering tank 4 rotates steadily at the very low speed when thewashings Q are placed in the dewatering tank 4 in a manner of beingbiased in the circumferential direction X, the rotating speed of themotor 6 is changed like that shown in FIG. 6. Specifically, the washingsQ are moved toward the upper side Z1 when going to the deep positionfrom the front position, which causes a burden to the motor 6.Therefore, the rotating speed of the motor 6 is reduced. On thecontrary, the rotating speed of the motor 6 is increased due to thereduction of the previous burden when the washings Q are moved to thefront position from the deep position. Therefore, it can be known that,the washings Q are located at the front position when the rotating speedof the motor 6 is maximum, and the washings Q are located at the deepposition when the rotating speed of the motor 6 is minimum. In this way,since the dewatering tank 4 rotates at very low speed, a biased positionof the washings Q in the dewatering tank 4 in the circumferentialdirection X can be detected according to the rotating speed of the motor6.

FIG. 7 is a flow chart illustrating a control action at the preparationstage of dewatering operation.

According to the above contents, the control part 30 causes the motor 6to start to rotate at very low speed at the dewatering preparationstage, so that the dewatering tank 4 rotates at very low speed (stepS1). It shall be noted that, prior to the dewatering operation, if thewater in the outer tank 3 and the dewatering tank 4 is discharged afterthe washings Q are rinsed, the motor 6 starts to rotate at the veryspeed in step S1 according to a current station that the discharging isfinished. When the motor 6 rotates at the very low speed, the controlpart 30 detects the biased position of the washings Q in the dewateringtank 4 in real time according to an output result from the rotatingspeed reading apparatus 37 (step S2). Next, the control part 30 brakesthe motor to stop the rotation of dewatering tank 4 immediately beforethe washings Q reach at the deep position according to the detectedbiased position (step S3).

If the rotation of the dewatering tank 4 is stopped when the washings Qbiased in the dewatering tank 4 are located at a side opposite to theliquid in the balancing ring 19 relative to the central axis 17, thewashings Q will finally arrive at a side same as that of the liquid inthe balancing ring 19 because the rotation might not be stopped timelyor the dewatering tank 4 might rotate again due to inertia when thebrake is relieved after the dewatering tank 4 is stopped.

In view of this, the control part 30 causes the dewatering tank 4 tostop rotating immediately before the washings Q biased in the dewateringtank 4 is located at a side opposite to, relative to the central axis17, the liquid biased towards the lower side Z2 in the balancing ring19. Therefore, after the dewatering tank 4 is stopped, the washings Qbiased in the dewatering tank 4 and the liquid biased towards the lowerside Z2 in the balancing ring 19 are maintained at a state of beinglocated at roughly opposite sides relative to the central axis 17. Inaddition, since the dewatering tank 4 is supported through a one-waybearing in a unidirectional rotation manner, the stopped dewatering tank4 does not reverse, and is in a static state. After such preparationstage, when the dewatering tank 4 rotates to dewater, the dewateringtank 4 rotates in a state that the liquid in the balancing ring 19 andthe washings Q are roughly balanced. Thus, the eccentric rotation of thebiased dewatering tank 4 can be inhibited early.

Next, description is made to the first acceleration stage aftersubjecting to the dewatering preparation interval. It shall be notedthat, since the liquid in the balancing ring 19 is not biased toward thelower side Z2 due to an effect of the centrifugal force after the firstacceleration stage, the liquid substantively does not cause theeccentric rotation of the dewatering tank 4.

FIG. 8 is a flow chart illustrating a control action in the firstacceleration stage. By referring to FIG. 8, after the dewateringpreparation interval, the control part 30 causes the motor 6 toaccelerate to reach a target rotating speed (i.e., 120 rpm) so as tostart the dewatering operation (step S11). Once the above interruption Wis inputted (“yes” in step S12), the control part 30 enables a countvalue n with an initial value “zero” to add by 1 (+1) (step S13). Then,the control part 30 starts detection 1 in the first acceleration stage(step S14). When detection 1 is “OK” (“yes” in step S15), that is, undera condition that the control part 30 determines that the washings Q arenot biased, the control part 30 resets the count value n to zero (stepS17) if detection 1 is ended (“yes” in step S16). Then, when therotating speed of the motor 6 reaches 120 rpm (“yes” in step S18), thecontrol part 30 causes the motor 6 to rotate steadily at 120 rpm (stepS19).

FIG. 9A and FIG. 9B are flow charts illustrating a control actionregarding detection 1. By referring to FIG. 9A, the control part 30starts detection 1 in the above step S14, and once the interruption W isinputted (“yes” in step S21), a timing value A_(n) is obtained (stepS22). The timing value A_(n) is referred to as A_(n) below. A_(n) is theinterval I between the inputted interruption W and the previousinterruption W (referring to FIG. 3) and is a positive value measured bythe timer 33. Under a condition that there does not exist a previousinterruption W, the interval I from a start time of detection 1 to theinitial interruption W is A_(n). It shall be noted that, when theinterruption W is inputted, since the count value n is added by 1 (stepS13) while A_(n) is obtained, a suffix “n” in the A_(n) is consistentwith the count value n added by 1. Therefore, for example, when theinitial interruption W is inputted, the count value n becomes 1, andA_(n) becomes A₁. When a next interruption W is inputted, the countvalue n becomes 2, and A_(n) becomes A₂.

Next, the control part 30 calculates a moving average value B_(n) ofA_(n) (step S23). Hereinafter, the moving average value B_(n) issometimes referred to as B_(n). B_(n) is a value obtained by dividing asumming value of A_(n) and previous A_(n−1)˜A_(n−5) by 6. Herein, 6 isdivided so as to be in combination with the situation that there existssix interruptions W during the period R from the time that the pulse Pdisappears to the time that the next pulse P is produced and thendisappears (referring to FIG. 3).

Next, the control part 30 calculates a moving average value C_(n) ofB_(n) (step S24). Hereinafter, the moving average value C_(n) issometimes referred to as C_(n). C_(n) is a value obtained by dividing asumming value of B_(n) and previous B_(n−1)˜B_(n−5) by 6.

In an acceleration state of the motor 6 for accelerating to the targetrotating speed, the control part 30 enables the count value n to beadded by 1 in step S13 (referring to FIG. 8) once the interruption W isinputted, and obtains C_(n) successively in step S24. Therefore, infact, the operation for adding the count value n by 1 and the operationfor obtaining C_(n) are conducted simultaneously. That is, the controlpart 30 enables the count value n to be added by 1 every time C_(n) isobtained.

According to experiences, the obtained A_(n)˜C_(n) are not stable untilthe count value n reaches a specified starting value (“no” in step S25),and the count value n is inapplicable to detection 1. The starting valuerefers to, such as, 75, in the present embodiment. When the count valuen reaches the starting value (“yes” in step S25), the control part 30calculates a difference D_(n) obtained by subtracting the previousC_(n−1) from C_(n) (step S26). Then, the control part 30 calculates amoving average value E_(n) of the difference D_(n) (step S27). Themoving average value E_(n) is a value obtained by dividing a summingvalue of the difference D_(n) and previous differences D_(n−1)˜D_(n−5)by 6. Hereinafter, the difference D_(n) is referred to as D_(n) and themoving average value E_(n) is referred to as E_(n).

With respect to respective meanings of D_(n) and E_(n), description ismade by taking C₁₁ (=(B₆+B₇+B₈+B₉+B₁₀+B₁₁)/6) and C₁₇(=(B₁₂+B₁₃+B₁₄+B₁₅+B₁₆+B₁₇)/6) as an example. E₁₇, the count value n ofwhich is consistent with that of C₁₇, is a value obtained by dividingD₁₂˜D₁₇ by 6. E₁₇ may be expressed with C_(n) as shown in the followingformula (1), and may be expressed with B_(n) as shown in the followingformula (2).

$\begin{matrix}\begin{matrix}{E_{17} = {\left( {D_{12} + D_{13} + D_{14} + D_{15} + D_{16} + D_{17}} \right)\text{/}6}} \\{= \left( {C_{12} - C_{11} + C_{13} - C_{12} + C_{14} - C_{13} + C_{15} - C_{14} +} \right.} \\{\left. {C_{16} - C_{15} + C_{17} - C_{16}} \right)\text{/}6} \\{= {\left( {{C\; 17} - {C\; 11}} \right)\text{/}6}}\end{matrix} & {{Formula}\mspace{14mu} (1)} \\{E_{17} = {\left( {\left( {B_{12} + B_{13} + B_{14} + B_{15} + B_{16} + B_{17}} \right) - \left( {B_{6} + B_{7} + B_{8} + B_{9} + B_{10} + B_{11}} \right)} \right)\text{/}36}} & {{Formula}\mspace{14mu} (2)}\end{matrix}$

As mentioned above, with respect to the total three Hall IC40, thereexists six interruptions W during the period R of one Hall IC40 from thetime at which a pulse P disappears to the time at which the next pulse Pis produced and then disappears (referring to FIG. 3). The installationerror of the Hall IC40 can be eliminated through B_(n). Moreover,according to Formula (2), E_(n) is equivalent to a difference of asumming value of B_(n)˜B_(n+5) related to six interruptions W producedwhen a certain NS group passes one Hall IC40 and a summing value ofB_(n+6)˜B_(n+11) related to six interruptions W produced when a next NSgroup passes the Hall IC40. An error due to a relevant position of theadjacent NS groups can be roughly eliminated through E_(n) calculatedwith multiple B_(n).

FIG. 10 is a diagram illustrating a relationship between a count value nand C_(n), where a horizontal axis indicates the count value n, and avertical axis indicates C_(n). By referring to FIG. 10, although A_(n)decreases with a rotating speed increase caused by the acceleration ofthe motor 6, the change of A_(n) is disordered due to the installationerror of the NS group and the installation error of each Hall IC40. Theactual A_(n) increases and decreases as shown by the dotted line. B_(n)is obtained through the moving average in S23 with the installationerror of each Hall IC40 being eliminated, and C_(n) is obtained throughthe moving average in S24 with the noise of B_(n) being eliminated.Then, D_(n) is obtained through C_(n), and E_(n) is obtained throughD_(n). A_(n), B_(n), C_(n), D_(n) and E_(n) are relevant informationvalues regarding the rotation state of the motor 6.

In the case that the dewatering tank 4 does not rotate eccentricallybecause the washings Q are not biased, C_(n) should decrease with theincrease of the rotating speed of the motor 6 (referring to an arrow ina dot and dash line), as shown by a solid line in FIG. 10. In addition,since the moving average value of A_(n) is B_(n) and the moving averagevalue of B_(n) is C_(n), A_(n) and B_(n) should also decrease with theincrease of the rotating speed of the motor 6 although both of A_(n) andB_(n) have noise respectively.

In the case that the dewatering tank 4 does not rotate eccentrically,since C_(n) always decreases in the acceleration process of the motor 6,the difference D_(n) obtained by subtracting the previous C_(n−1) fromC_(n) becomes not greater than zero, and the moving average value E_(n)of D_(n) also becomes not greater than zero. By referring to FIG. 9B, ifE_(n) is not greater than zero (“yes” in step S28), the control part 30enables a variable F_(n) to be zero (step S29). On the other hand, inthe case that the dewatering tank 4 rotates eccentrically because thewashings Q in the dewatering tank 4 are biased, C_(n) which shoulddecrease may be changed and increase with the increase of the rotatingspeed of the motor 6. In this case, D_(n) and E_(n) at a time, at whichC_(n) increased, become greater than zero (“no” in step S28), and thecontrol part 30 sets the variable F_(n) as E_(n) per se (step S30).

The control part 30 calculates an accumulated value G (=F₁+F₂+ . . . )of F_(n) once F_(n) is obtained (step S31). The accumulated value G isalso an accumulated value of the moving average value E_(n) of thedifference D_(n) between C_(n) and C_(n−1) in the case that C_(n) isgreater than the previous C_(n−1).

FIG. 11 is a diagram illustrating a relationship between the count valuen and the accumulated value G, where a horizontal axis indicates thecount value n, and a vertical axis indicates the accumulated value G. Inthe case that the motor 6 accelerates while the dewatering tank 4eccentrically rotates continuously, the accumulated value G increasesstepwise, as shown in FIG. 11. With respect to the accumulated value G,first thresholds are determined according to each specified count valuen. The first thresholds are correlated with the count value n and storedin the memory 32 (referring to FIG. 2). The first thresholds arepositive values.

Returning to FIG. 9B, when the accumulated value G for count value nwith a specified value reaches a first threshold for count value n withthe specified value (“yes” in step S32), the control part 30 sets thedetection result as NG, and determines that the dewatering tank 4 islargely eccentric and the washings Q are biased (step S33).

On the other hand, if the accumulated value G is less than thecorresponding first threshold (“no” in step S32), the control part 30sets the detection result as OK, and determines that the washings Q arenot biased (step S34). Then, the control part 30 carries out stepsS21˜S34 repeatedly, until the count value n becomes an end valueindicating that the first acceleration stage is ended (“no” in stepS35). The end value of the count value n in the present embodiment is,for example, 245. When the count value n becomes the end value (“yes” instep S35), detection 1 is ended by the control part 30 (step S36). Theprocesses of steps S21˜S34 are equivalent to the process of the abovestep S15, and the processes of steps S35˜S36 are equivalent to theprocess of the above step S16 (referring to FIG. 8).

FIG. 12 is a flow chart illustrating a control action in the case thatthe detection result is NG. By referring to FIG. 12, the control part 30causes the motor 6 to stop rotating (step S41), i.e. causes thedewatering tank 4 to stop rotating, when the detection result isdetermined as NG. Thus, in the case that the washings Q in thedewatering tank 4 are biased, the eccentric rotation of the dewateringtank 4 can be inhibited early when the motor 6 is in the accelerationstate.

Especially, prior to calculating the accumulated value G, the controlpart 30 first corrects a calculation basis (i.e., A_(n)) of theaccumulated value G through performing the moving average in step S23and step S24 repeatedly. Therefore, C_(n) obtained as a correctionresult becomes a high precision value with the error being eliminated.Therefore, an accumulated value G with high precision is calculatedaccording to C_(n), the precision of which is improved through thecorrection, and the bias of the washings Q is detected with highprecision through the accumulated value G, thus the eccentric rotationof the dewatering tank 4 can be inhibited early.

After the dewatering tank 4 stops rotating, the control part 30determines whether the current state is a state before the dewateringoperation is restarted (step S42). Restarting of the dewateringoperation refers to a restarting process, through which the control part30 starts the dewatering operation again by enabling the dewatering tank4 to rotate again immediately after the dewatering tank 4 is caused tostop rotating to suspend the dewatering operation. Sometimes, therestarting process may also be conducted even if the biasing of thewashings Q is small.

Before the restarting of the restarting process is implemented (“yes” instep S42), the control part 30 performs the restarting process (stepS43). It shall be noted that, prior to the restarting process, adrainage can be first conducted in the outer tank 3. In the case thatthe drainage pipeline 15 is jammed with foams, the foams can bedischarged outside of the drainage pipeline 15 through the drainageherein, and thus, the situation that the drainage pipeline 15 is jammedwith the foams can be eliminated.

If it is not a state before restarting (“no” in step S42), the controlpart 30 performs a correction process (step S44). In the correctionprocess, the control part 30 closes the drainage valve 16 and opens thefeeding valve 14 so as to feed water into the dewatering tank 4 to aspecified water level, so that the washings Q in the dewatering tank 4are immerged into water and are easy to loosen. In this state, thecontrol part 30 causes the washings Q attached to the internalcircumferential surface of the dewatering tank 4 to peel off and stir bycausing the dewatering tank 4 and the rotary wing 5 to rotate, therebycorrecting the biasing of the washings Q in the dewatering tank 4.

In this way, the control part 30 performs either the restarting processor the correction process alternatively in the case that the dewateringtank 4 has stopped rotating. If the biasing of the washings Q is smallenough so that the dewatering tank 4 does not rotate eccentrically, thedewatering is started again through the restarting process. Therefore, atime required in the whole dewatering process can be shortened as far aspossible. If the biasing of the washings Q is large enough so that thedewatering tank 4 rotates eccentrically again in the next dewateringprocess, the biasing of the washings Q can be reliably corrected throughthe correction process.

After performing the restarting process for a specified number (which is1 herein) and enabling the dewatering tank 4 to stop rotating (“no” instep S42), the control part 30 selects to not perform the restartingprocess and selects to perform the correction process (step S44). Thatis, in the case that the restarting process has been performed for thespecified number and the dewatering tank 4 has stopped rotating, thebiasing of the washings Q is large and needs to be corrected. In thiscase, the correction process is quickly performed rather than spendingtime on the restarting process and stopping the rotation of thedewatering tank 4. Therefore, the biasing is corrected reliably.Therefore, the eccentric rotation of the dewatering tank 4 can beinhibited early. It shall be noted that, in the present embodiment,although the specified time is set as 1, it can also be set as more than2.

Then, description is made to the second acceleration stage after thesteady rotation at 120 rpm. FIG. 13 is a flow chart illustrating acontrol action in the third acceleration stage. By referring to FIG. 13,the control part 30 causes the motor 6 to accelerate to a targetrotation speed of 240 rpm at the second acceleration stage (step S51).The control part 30 enables the count value n to add by 1 (step S53)once the interruption W is inputted (“yes” in step S52). It shall benoted that, the count value n at the beginning of the secondacceleration stage is zero.

Next, in the second acceleration stage, the control part 30 startsdetection 2 (step S54). In the case that detection 2 is OK (“yes” instep S55), that is, in the case that the control part 30 determines thatthe washings Q are not biased in the second acceleration stage, thecontrol part 30 resets the count value n to zero (step S57) at the endof detection 2 (“yes” in step S56). Then, when the rotating speed of themotor 6 reaches 240 rpm (“yes” in step S58), the control part 30 causesthe motor 6 to rotate steadily at 240 rpm (step S59).

The content of detection 2 is the same as that of detection 1.Therefore, the processes of above steps S21˜S34 are equivalent to theprocess of step S55, and the processes of step S35 and S36 areequivalent to the process of step S56 (referring to FIG. 9B). The firstthreshold in detection 2 is set as to be different from that indetection 1. In addition, with respect to detection 2, since therotating speed of the motor 6 is higher than that in detection 1, thestarting value in step S25 (referring to FIG. 9A) is accordingly lessthan the starting value in detection 1, which is, for example, 17 in thepresent embodiment. In the case that the detection result of detection 2is NG (“no” in step S55), that is, in the case that the control part 30determines that the washings Q in the dewatering tank 4 are biased, thecontrol part 30 performs the processes of steps S41˜S44 as it did indetection 1 (referring to FIG. 12).

It shall be noted that, with respect to the dewatering operation underthe restarting process after detection 2, the duration of the steadyrotation at 120 rpm (referring to FIG. 4) can be shortened to be shorterthan the duration of the steady rotation at 120 rpm of the previousdewatering operation which is stopped. With respect to the restartingprocess, since the washings Q are attached to the internalcircumferential surface of the dewatering tank 4 to a certain extent andin a state of roughly being dewatered, the duration of the steadyrotation at 120 rpm can be shortened. Thus, the time of the dewateringoperation can be shortened.

Next, description is made to the third acceleration stage after thesteady rotation at 240 rpm. FIG. 14 is a flow chart illustrating acontrol action in the third acceleration stage. By referring to FIG. 14,the control part 30 causes the motor 6 to accelerate to a targetrotating speed 800 rpm in the third acceleration stage (step S61). Thecontrol part 30 enables the count value n to be added by 1 (step S63)once the interruption W is inputted (“yes” in step S62). In addition,the count value n at the beginning of the third acceleration stage iszero.

In the third acceleration stage, the control part 30 starts detection 3(step S64). Next, in the case that detection 3 is OK (“yes” in stepS65), that is, in the case that the control part 30 determines that thewashings Q are not biased, the control part 30 stops detection 3 whenthe rotating speed of the motor 6 reaches 800 rpm (“yes” in step S66),and resets the count value n as zero, so that the motor 6 rotatessteadily at 800 rpm to continue to dewater (step S67).

The content of detection 3 is substantively the same as those ofdetections 1 and 2. Therefore, the processes of the above steps S21˜S34are equivalent to the process of step S65 (referring to FIG. 9A and FIG.9B). The first threshold in detection 3 is set as to be different fromthose of detections 1 and 2 respectively. It shall be noted that, thestarting value in step S25 (referring to FIG. 9A) in detection 3 is thesame as that in detection 2. In the case that the detection result ofdetection 3 is NG (“no” in step S65), that is, in the case that thecontrol part 30 determines that the washings Q in the dewatering tank 4are biased, the control part 30 also performs the processes of stepsS41˜S44 as it does in detections 1 and 2 (referring to FIG. 12).

It shall be noted that, with respect to dewatering operation under therestarting process after detection 3, as described regarding detection2, the duration of the steady rotation at 120 rpm may be shortened to beshorter than the duration of the steady rotation at 120 rpm of theprevious dewatering operation which is stopped. Moreover, the differencebetween detection 3 and detections 1, 2 lies in: after n becomes the endvalue in step S35 (referring to FIG. 9B), the processes in step S21˜stepS34 may also be repeated during the period that the rotating speed ofthe motor 6 reaches 800 rpm. At the beginning of repeating suchprocesses, respective values of n and A_(n)˜G are reset to zero.

As described above, in detection 1 of the first acceleration stage,detection 2 of the second acceleration stage and detection 3 of thethird acceleration stage, the control part 30 acquires informationvalues of A_(n)˜E_(n) and the like respectively, enables the count valueto be added by 1 so as to calculate the accumulated value G. When theaccumulated value G reaches a corresponding first threshold, the controlpart 30 determines that the washings Q are biased in the dewatering tank4 and causes the dewatering tank 4 to stop rotating. That is, since thedetection of the biasing of the washings Q begins in the firstacceleration stage after the motor 6 starts to rotate, eccentricrotation of the dewatering tank 4 may be inhibited early. Moreover,since the detection of the biasing of the washings Q is carried out inthree stages in a sequence of the first acceleration stage, the secondacceleration stage, and the third acceleration stage, the biasing of thewashings Q can be reliably detected, so that eccentric rotation of thedewatering tank 4 may be inhibited as early as possible.

In detection 3, the control part 30 executes detection in a first mode.As described above, In the detection in the first mode, the biasing ofthe washings Q in the dewatering tank 4 is detected according to whetherthe accumulated value G reaches the first threshold. The control part 30may also execute a detection in a second mode rather than executing thedetection in the first mode. In the detection in the second mode, thebiasing of the washings Q is detected according to whether a variationof the accumulated value G reaches a third threshold. Different from thefirst threshold, the third threshold is preset and stored in the memory32 (referring to FIG. 2). The third threshold is a positive value. Likein the third acceleration stage, when the rotating speed of the motor 6rises to a certain extent, for example, 400 rpm, an eccentric state ofthe washings Q in the dewatering tank 4 may be deteriorated becausewater of the washings Q is removed due to previous dewatering. As aresult, the vibration of the dewatering tank 4 becomes larger. On theother hand, as the characteristics of the accumulated value G, althoughthe accumulated value G sharply increases when the rotating speed of themotor 6 is low, the accumulated value G increases slowly as the rotatingspeed approaches the target rotating speed.

Thus, merely for the detection in the first mode, when the rotatingspeed rises to some extent, the accumulated value G may be lower thanthe first threshold no matter whether the vibration of the dewateringtank 4 is large or small, so that the dewatering tank 4 fails to stoprotating. Accordingly, both of the detections in the first mode and thesecond mode may be executed. As for the detection in the second mode,when the variation of the accumulated value G, i.e., a variation degreeof the accumulated value G, reaches the third threshold, the controlpart 30 determines that the washings Q are biased and causes thedewatering tank 4 to stop rotating. Thus, the accumulated value G mayalways be small and fails to reach the first threshold no matter whetherthe dewatering tank 4 is in a state of large amplitude vibration, andwith such situation, state variation of the washings Q during dewateringmay also be sensitively reflected by focusing on the variation of theaccumulated value G. Therefore, the eccentric rotation of the dewateringtank 4 can be reliably inhibited early. Certainly, the detection in thesecond mode not only can be executed in detection 3, but also can beexecuted in detection 1 and detection 2.

Next, description is made to detection 4 which is executed in parallelwith the detection 3 in the third acceleration stage. Detection 4consists of detection 4-1 and detection 4-2. Detections 1-3 aredetections for detecting the biasing of the washings Q by usinginterruption W related to the motor 6 in an acceleration state. Relativeto this, detection 4-1 and detection 4-2 are detections for detectingthe biasing of washings Q by using the duty ratio. FIG. 15 is a flowchart illustrating schemas of detection 4-1 and detection 4-2.

Referring to FIG. 15, as the third acceleration stage, the control part30 causes the motor 6 to accelerate from 240 rpm to 800 rpm in step S61(referring to FIG. 14).

In a state that the motor 6 is accelerated, when the rotating speed ofthe motor 6 reaches 300 rpm, the control part 30 acquires a duty ratioof the voltage applied to the motor 6 at this moment as α value (stepS71). The rotating speed 300 rpm does not refer to a rotating speed in astate that water is stored in the dewatering tank 4, but refers to arotating speed which is not influenced by eccentricity of the dewateringtank 4 most. Thus, the α value at 300 rpm is the duty ratio in a statethat it is not influenced by eccentricity of the dewatering tank 4 most,but only is influenced by a load of the washings Q.

Moreover, in a state that the motor 6 continues to accelerate, during aperiod in which the rotating speed rises from 600 rpm to 729 rpm, thecontrol part 30 implements detection 4-1 (step S72). Under a conditionthat detection 4-1 is not OK (“no” in step S72), that is, under acondition that the control part 30 determines that the washings Q arebiased, the control part 30 executes the processes in step S41˜step S44as it does in detections 1˜3 (referring to FIG. 12). It shall be notedthat, as described in detection 2 and detection 3, with respect to thedewatering operation in the restarting process after detection 4-1, theduration of the steady rotation at 120 rpm may be shortened to beshorter than the duration of the steady rotation at 120 rpm of theprevious dewatering operation which is stopped.

On the other hand, under a condition that detection 4-1 is OK (“yes” instep S72), that is, under a condition that the control part 30determines in detection 4-1 that the washings Q are not biased, thecontrol part 30 continues to implement detection 4-2 in a state that themotor 6 continues to accelerate from 730 rpm (step S77).

Under a condition that detection 4-2 is OK (“yes” in step S77), that is,under a condition that the control part 30 determines in detection 4-2that the washings Q are not biased, the control part 30 causes the motor6 to stably rotate at 800 rpm after accelerating the motor 6 to thetarget rotating speed of 800 rpm, so as to cause the washings Q to bedewatered continuously (step S78).

On the other hand, under a condition that detection 4-2 is not OK (“no”in step S77), that is, under a condition that the control part 30determines that the washings Q are biased, the control part 30 causesthe motor 6 to stably rotate at a rotating speed less than 800 rpm, soas to cause the washings Q to be dewatered continuously (step S79).

Next, detection 4-1 and detection 4-2 are described in detailrespectively.

FIG. 16 is a flow chart illustrating a control action with respect todetection 4-1. Referring to FIG. 16, in the state that the motor 6continues to accelerate after step S71 (referring to FIG. 15), thecontrol part 30 starts to carry out detection 4-1 (step S80) as therotating speed of the motor 6 reaches 600 rpm.

Next, the control part 30 starts to count through the counter 34 (stepS81), and initializes the counter 34 every 0.3 s so as to count within0.3 s (step S82 and step S83).

The control part 30 acquires the rotating speed of the motor 6 at thetime of each counting and a duty ratio d_(m)(m: a count value) of thevoltage applied to the motor 6 at the time of counting (step S84). Thatis, the control part 30 acquires the rotating speed and the duty ratiod_(m) of the motor 6 at specified moment in the third acceleration stagein which the rotating speed of the motor 6 rises from 240 rpm to 800rpm. The duty ratio d_(m) is an information value related to therotation state of the motor 6.

Moreover, in step S84, the control part 30 calculates a correction valueB_(m) according to the following formula (3), where B_(m) is obtained bycorrecting the duty ratio d_(m) with the α value. It shall be noted thatX and Y in the formula (3) are constants solved through experiments andthe like. Different from simple ratio calculation, a weight is changedthrough the formula (3), so that the duty ratio d_(m) is corrected, anddetection 4-1 may be executed with good accuracy through the obtainedcorrection value B_(m).

B _(m) =d _(m)−(α×X+Y)  formula (3)

Moreover, in step S84, the control part 30 calculates a movingaccumulated value C_(m) (m: count value) of the correction value B_(m).The moving accumulated value C_(m) is a value obtained by summing 5consecutive correction values B_(m) in a counting sequence.Additionally, as for a certain moving accumulated value C_(m) and amoving accumulated value C_(m−1) previous to C_(m), the last 4correction values B_(m) among the 5 correction values B_(m) for formingthe moving accumulated value C_(m−1) and the front 4 correction valuesB_(m) among the 5 correction values B_(m) for forming the movingaccumulated value C_(m) are same values respectively. It shall be notedthat the number of the correction values B_(m) for forming the movingaccumulated value C_(m) is not limited to 5. The moving accumulatedvalue C_(m) is a specified index value transformed from the duty ratiod_(m) by the control part 30.

Next, the control part 30 calculates a second threshold (step S85)related to the moving accumulated value C_(m) according to the followingformula (4). The second threshold is a positive value.

The second threshold=(rotating speed)×a+b  formula (4)

a and b in the formula (4) are constants solved through experiments andthe like and stored in the memory 32. Moreover, the constants a, b aredifferent depending on the rotating speed of the motor 6 at the currentmoment and a selected dewatering condition. Thus, as for the secondthreshold herein, multiple values exist at the same rotating speed. Itshall be noted that the second threshold is a value not influenced bythe α value, and this case is further defined through the formula (4).

Then, the control part 30 confirms whether the rotating speed of themotor 6 at the current moment is less than 730 rpm (step S86).

Under a condition that the rotating speed of the motor 6 at the currentmoment is less than 730 rpm (“yes” in step S86), the control part 30determines whether a newest moving accumulated value C_(m) falls in therange of detection 4-1 (step S87).

FIG. 17 is a diagram illustrating a relationship between the rotatingspeed and the moving accumulated value C_(m) in combination withdetection 4-1 and detection 4-2. In FIG. 17, a horizontal axisrepresents the rotating speed (unit: rpm), and a longitudinal axisrepresents the moving accumulated value C_(m). Referring to FIG. 17, thesecond thresholds calculated in step S85 are set to be two thresholdsincluding an upper second threshold represented by a dot dash line and alower second threshold represented by a double dot dash line. The uppersecond threshold is higher than the lower second threshold. The uppersecond threshold and the lower second threshold vary along with therotating speed.

As for the dewatering conditions, there exists the following threedewatering conditions: carrying out the dewatering operation after“water storage rinsing” of rinsing the washings Q with the water storedin the dewatering tank 4; “water splashing and dewatering” of carryingout the dewatering operation by draining water when splashing the waterto the washings Q; the above “restarting process”, etc. The dewateringconditions are selected by the user through operating the operation part10, and the selection is received by the control part 30. In thedewatering operation after washing operation and water storage rinsing,of the motor 6 is hard to accelerate since the washings Q contain agreat quantity of water, while under the condition of water splashingand dewatering and the restarting process, acceleration of the motor 6may be realized with very tiny force because the water is removed fromthe washings Q to some extent.

In the dewatering operation after the washing operation and waterstorage rinsing, the control part 30 uses the upper second thresholdhigher than the lower second threshold because it is difficult toexecute detection with the lower second threshold. On the other hand, inthe dewatering operation after water splashing and dewatering and therestarting process, the control part 30 uses the lower second thresholdlower than the upper second threshold because the detection is notaccurate if the upper second threshold is used. Thus, under either thecondition that the washings Q contain a great quantity of water or underthe condition that the water of the washings Q are removed to someextent, detection 4-1 is executed with the second threshold suitable forthe respective conditions.

Moreover, based on the objective same as a difference between suchdewatering conditions, under the condition that the load of the washingsQ in the dewatering tank 4 is large, the control part 30 uses the uppersecond threshold higher than the lower second threshold in detection 4-1because it is difficult to execute the detection with the lower secondthreshold. Moreover, under the condition that the load of the washings Qin the dewatering tank 4 is small, the control part 30 uses the lowersecond threshold lower than the upper second threshold in detection 4-1because the detection is not accurate if the upper second threshold isused. Thus, detection 4-1 is executed with the second threshold suitablefor different loads of the washings Q respectively.

It shall be noted that in FIG. 17, although the two second thresholdsincluding the upper second threshold and the lower second threshold areillustrated, more than 3 second thresholds may also be set according tovarious dewatering conditions and the loads.

Moreover, compared with the condition that the washings Q are not biaseddue to smaller eccentricity (referring to a solid line in FIG. 17),under the condition that the washings Q are biased due to largereccentricity (referring to the dotted lines in FIG. 17), the movingaccumulated value C_(m) at each rotating speed is larger. If thewashings Q are greatly biased, the moving accumulated value C_(m) islarger than the set second threshold, i.e. a corresponding one of theupper second threshold and the lower second threshold.

Returning to FIG. 16, when the newest moving accumulated value C_(m)reaches the second threshold for a corresponding moment, the controlpart 30 determines that the washings Q are biased in the dewatering tank4 and the moving accumulated value C_(m) falls in the range of detection4-1 (“yes” in step S87).

When the control part 30 determines that the moving accumulated valueC_(m) falls in the range of detection 4-1 (“yes” in step S87), theprocesses in steps S41˜S44 will be executed (referring to FIG. 12). Theprocesses in steps S80˜S87 are included in the above step S72 (referringto FIG. 15).

Next, if it is determined in detection 4-1 that the washings Q are notbiased, the control part 30 ends detection 4-1 and then starts detection4-2 (step S88) when the rotating speed of the motor 6 reaches 730 rpm(“no” in step S86).

FIG. 18 is a flow chart illustrating a control action regardingdetection 4-2. Referring to FIG. 18, in the case that the motor 6continues to accelerate, the control part 30 starts detection 4-2 (stepS88) as the rotating speed of the motor 6 reaches 730 rpm.

Next, the control part 30 starts to count through the counter 34 (stepS89), and initializes the counter 34 per 0.3 s so as to carry outcounting within each 0.3 s (steps S90˜S91).

Similar to step S84 in detection 4-1, upon each counting, the controlpart 30 acquires the rotating speed of the motor 6 at the time of eachcounting and the duty ratio d_(m) of the voltage applied to the motor 6at the time of counting, and calculates the correction value B_(m) andthe moving accumulated value C_(m) (step S92).

Next, the control part 30 calculates the second threshold (step S93)related to the moving accumulated value C_(m) according to the formula(4). The constants “a”, “b” included in the formula are same as thoseused in detection 4-1, and are different depending on the rotating speedof the motor 6 at the current moment and the selected dewateringcondition. Therefore, at the same rotating speed, the second thresholdherein may have multiple values like the upper second threshold and thelower second threshold described above.

Next, the control part 30 confirms whether the rotating speed of themotor 6 at the current moment reaches the target rotating speed (800rpm) (step S94).

In the case that the rotating speed of the motor 6 at the current momentdos not reach the target rotating speed (“yes” in step S94), the controlpart 30 determines whether the newest moving accumulated value C_(m)falls in the range of the detection 4-2 (step S95) as it does indetection 4-1 (step S87).

Specifically, by referring to FIG. 17, compared with the situation thatthe washings Q are not biased due to small eccentricity (referring tothe solid line in FIG. 17), in the situation that the washings Q arebiased due to larger eccentricity (referring to the dotted line in FIG.17), the moving accumulated value C_(m) for each rotating speed islarger. If the washings Q are greatly biased, the moving accumulatedvalue C_(m) is larger than the set second thresholds, i.e., acorresponding one of the upper second threshold and the lower secondthreshold.

Returning to FIG. 18, if the newest moving accumulated value C_(m) isnot less than the set second threshold, the control part 30 determinesthat the washings Q are biased in the dewatering tank 4 and the movingaccumulated value C_(m) falls in the range of detection 4-2 (“yes” instep S95).

When it is determined that the moving accumulated value C_(m) falls inthe range of detection 4-2 (“yes” in step S95), the control part 30acquires the rotating speed L of the motor 6 (step S96) at the judgedtime point, i.e., the time point when it is detected in detection 4-2that the washings Q are biased.

Next, the control part 30 causes the motor 6 to stably rotate at theacquired rotating speed L, strictly speaking, a rotating speed obtainedby rounding off the digit in the units position of the rotating speed L,so that the washings Q are continuously dewatered (step S79). At thismoment, the control part 30 prolongs dewatering time at the rotatingspeed L so as to obtain a dewatering effect same as that obtainedthrough the dewatering at the original target rotating speed of 800 rpm.

Next, if it is determined in detection 4-2 that the washings Q are notbiased, the control part 30 ends detection 4-2 and causes the motor 6 tostably rotate at 800 rpm so as to continue to dewater the washings Q(the above step S78) when the rotating speed of the motor 6 reaches thetarget rotating speed (“no” in step S94).

In this way, in the third acceleration stage, the biasing of thewashings Q in the dewatering tank 4 is double detected in a modeadopting information values (such as C_(n)) and the first threshold(i.e., detections 1˜3), and a mode adopting the duty ratio d_(m) and thesecond thresholds (i.e., detection 4), so that eccentric rotation of thedewatering tank 4 may be reliably inhibited early.

The present disclosure is not limited to the embodiments as describedabove, but various changes may be made within a scope recorded in theclaims.

FIG. 19 is a flow chart illustrating a first modification of the controlaction of detection 3 in the third acceleration stage. It shall be notedthat, throughout the drawings including FIG. 19, same reference numeralsare used for same steps in other diagrams, and detailed description withrespect to the repeated steps is omitted. By referring to FIG. 19, likein detection 3, the control part 30 causes the motor 6 to accelerate tothe target rotating speed of 800 rpm (step S61), and enabled the countvalue “n” to be added by 1 (step S63) once the interruption W isinputted (“yes” in step S62). In the third acceleration stage, thecontrol part 30 starts detection 3 (step S64). Next, after it isdetermined that the detection 3 is OK (“yes” in step S65), the controlpart 30 ends detection 3 and resets the count value n to zero when therotating speed of the motor 6 reaches 800 rpm (“yes” in step S66), sothat the motor 6 stably rotates at 800 rpm, and dewatering continues(step S67).

In the first modification, during detection 3, the control part 30monitors a maximum G_(max) of G when the rotating speed of the motor 6is 250˜300 rpm (step S68). With respect to the maximum G_(max), aspecified reference value smaller than the first threshold is set andstored in the memory 32. If the maximum G_(max) does not exceed thereference value (“yes” in step S68), the control part 30 increases allof the second thresholds adopted in detection 4 (step S69).

That is, if the maximum G_(max) in detection 3 is less than thereference value, the dewatering tank 4 is at least in a state of beingin static balance. If the dewatering tank 4 is in a state that thebalance can be achieved statically or dynamically, although it is OK inboth of detection 3 and detection 4, longitudinal shaking of thedewatering tank 4 may also be sensitively detected by the concurrentlyexecuted detection 4 even if detection 3 is OK in a state of dynamicimbalance. Thus, it can be imagined that, if the C_(m) in detection 4 istoo large, the NG is caused. As a result, a poor condition of rotationstopping of the dewatering tank 4 may occur when detection 4 is carriedout although vibrations of the outer tank 3 and the dewatering tank 4are not large.

In order to prevent such poor condition, the control part 30 estimatesthat the vibrations of the outer tank 3 and the dewatering tank 4 arenot large and carries out a control of widening the second thresholds ofdetection 4 in step S69 as long as the maximum G_(max) in detection 3 isa low value below the reference value (“yes” in step S68). That is,error detection of detection 4 adopting the duty ratio d_(m) isprevented through detection 3.

FIG. 20 relates to a second modification of the control action indetection 3, and is a schematic diagram illustrating the interior of thedewatering tank 4 in the dewatering operation. For example, as shown inFIG. 20(a), the washings Q in the dewatering tank 4 might be arranged inthe dewatering tank 4 with a first washing Q1 and a second washing Q2being placed at a half of the dewatering tank 4 relative to the centralaxis 17. When the dewatering tank 4 rotates at the high speed of 800 rpmin the state, the dewatering tank 4 which is perfectly round initiallydeforms into an elliptic shape with a long edge formed in an oppositeposition direction of the first washing Q1 and the second washing Q2, asshown in FIG. 20 (b), and may contact with the circumferential wall 3Aof the outer tank 3. In order to prevent such problem, in the thirdacceleration stage, control of detection 3 of the second modificationshown in FIG. 21 may be implemented.

By referring to FIG. 21, the control part 30 causes the motor 6 toaccelerate to the target rotating speed of 800 rpm (step S61), andenables the count value n to be added by 1 (step S63) once theinterruption W is inputted (“yes” in step S62), as it does in detection3. In the third acceleration stage, the control part 30 starts detection3 (step S64). Next, after it is determined that detection 3 is OK (“yes”in step S65), the control part 30 ends detection 3, resets the countvalue n to zero and causes the motor 6 to steadily rotate at 800 rpm soas to continuously carry out dewatering (step S67) when the rotatingspeed of the motor 6 reaches 800 rpm (“yes” in step S66).

With respect to the maximum G_(max) in detection 1, a specified firstreference value smaller than the first threshold is set; with respect tothe maximum G_(max) in detection 2, a specified second reference valuesmaller than the first reference value is set; and with respect to themaximum G_(max) in detection 3 when the rotating speed of the motor 6 is250˜300 rpm, a specified third reference value smaller than the secondthreshold is set. The first reference value˜the third reference valueare stored in the memory 32.

As for detection 3 of the second modification, the previous maximumG_(max) in detection 1 never exceeds the first reference value (“yes” instep S101), the previous maximum G_(max) in detection 2 never exceedsthe second reference value (“yes” in step S102), and if the maximumG_(max) in detection 3 when the rotating speed of the motor 6 is 250˜300rpm never exceeds the third reference value (“yes” in step S103), thecontrol part 30 decreases all the second thresholds in detection 4 (stepS104).

That is, as long as the maximums G_(max) in respective detection amongdetections 1˜3 are smaller values below the corresponding referencevalues (“yes” in steps S101˜S103), the washings Q in the dewatering tank4 may be in a state of being evenly distributed in the dewatering tank 4or in a state of being tidily divided into two parts, as shown in FIG.20.

Thus, as long as the maximums G_(max) in respective detection amongdetections 1˜3 are smaller values below the corresponding referencevalues (“yes” in steps S101˜S103), the control part 30 decreases thesecond thresholds (step S104) if the washings Q in the dewatering tank 4are assumed to be in a state of being divided into two parts. Therefore,in detection 4 which is executed in parallel with detection 3, beforethe dewatering tank 4 deforms greatly toward the elliptic shape,detection 4-2 is enabled to be NG in step S95, so as to continue thedewatering operation at the rotating speed that makes the dewateringtank 4 not contact with the outer tank 3 in step S79 (referring to FIG.18).

As described above, in the modifications 1 and 2, the control part 30properly changes the second thresholds according to the maximum G_(max)of the accumulated values G in at least one of the first accelerationstage, the second acceleration stage and the third acceleration stage.Therefore, by changing the second thresholds to be suitable for thecurrent situation in the dewatering tank 4, the biasing of the washingsQ may be detected with high accuracy, so that eccentric rotation of thedewatering tank 4 is inhibited early. It shall be noted that, controlsof the modification 1 and the modification 2 may also be carried out inparallel.

FIG. 22 and FIG. 23 are flow charts illustrating a control action of athird modification in the dewatering operation. As described above, thedewatering machine 1 may electrically detect eccentric rotation of thedewatering tank 4 through detections 1˜4, and may also mechanicallydetect eccentric rotation of the dewatering tank 4 through the safetyswitch 36. That is, the biasing of the washings Q may be double detectedin an electric mode and a mechanical mode. The electric mode is a modeof carrying out detection based on a relationship of information values(i.e., the accumulated value G, the moving accumulated value C_(m), thefirst threshold and the second threshold) related to the rotation stateof the motor 6 at 800 rpm, and the mechanical mode is a mode of carryingout detection through contact between the safety switch 36 and the outertank 3. Therefore, either in the case that it is determined indetections 1˜4 that the washings Q are biased, or in the case that theeccentric rotation of the dewatering tank 4 is detected by the safetyswitch 36, the control part 30 causes the dewatering tank 4 to stoprotating.

Both of the mechanical mode and the electric mode are expected to detecteccentric rotation of the dewatering tank 4 at a same moment. However,in the dewatering machine 1 in a shipment stage, due to a differencebetween relative positions of the dewatering tank 4 and the safetyswitch 36 caused by an inclined error of the dewatering tank 4 amongindividuals of the dewatering machine 1, the first thresholds and thesecond thresholds of some dewatering machines 1 may not be proper. As aresult, there is a time deviation between the mechanical detection andthe electrical detection. Then, when the dewatering machine 1 is used,the deviation may be eliminated by correcting the first thresholds andthe second thresholds. Although description is made regarding correctingthe first thresholds in detection 1, the present disclosure is notlimited to only correcting the first thresholds in detection 1, and thefirst thresholds in detections 2˜3 and the second thresholds indetection 4 may also be corrected.

By referring to FIG. 22, the control part 30 causes the dewatering tank4 to rotate and start dewatering as the initial dewatering operationafter shipment starts (step S111). Along with starting of dewatering,detection 1 is carried out in the first stage. At this time, when thesafety switch 36 is switched to “on” (“yes” in step S112), the controlpart 30 uses the count value n at this time as n_(x) and uses theaccumulated value G at this time as G_(x) (step S113). The firstthreshold when the count value n is n_(x) is a value acquired bysubtracting the first specified value from n_(x) in the presentembodiment. The first specified value is a positive value.

The control part 30 determines whether a value obtained by subtractingG_(x) from the previous first threshold is above a second specifiedvalue J (step S114). The second specified value J is a positive value.In the case that a difference between the first threshold and the G_(x)is below the second specified value J (“no” in step S114), since theresubstantially does not exist a time deviation between the moment thatthe eccentric rotation is detected by detection 1 and the moment thatthe eccentric rotation is detected by the safety switch 36, the firstthreshold may be determined as proper, and the control part 30continuously carries out operation without changing the first threshold(step S115).

In the case that the difference between the first threshold and G_(x) isabove the second specified value J (“yes” in step S114), it can bedetermined that there exists a time deviation between the moment atwhich the eccentric rotation is detected by detection 1 and the momentat which the eccentric rotation is detected by the safety switch 36.Therefore, it can be determined that the moment at which the eccentricrotation is detected by detection 1 may be slower than that at which theeccentric rotation is detected by the safety switch 36. However, sincethe deviation may have occurred by accident, the control part 30 enablesa correction alternate value U, the factory default of which is zero, tobe added by 1 temporarily (step S116). If the correction alternate valueU added by 1 is smaller than a specified upper limit value (which is 3herein) (“no” in step S117), the control part 30 does not change thefirst threshold and enables operation to continue (step S118).

On the other hand, if the correction alternate value U added by 1reaches the upper limit value (“yes” in step S117), the current firstthreshold is not proper because there apparently exists a time deviationbetween the moment at which the eccentric rotation is detected bydetection 1 and the moment at which the eccentric rotation is detectedby the safety switch 36. Therefore, the control part 30 sets a valueacquired by subtracting the second specified value J from the firstthreshold as a new first threshold, so as to change and decrease thefirst threshold (step S119). Next, the control part 30 resets thecorrection alternate value U to zero (step S120) and enables operationto continue (step S121).

In this way, if a difference between the accumulated value G_(x) and thefirst threshold when eccentric rotation of the dewatering tank 4 isdetected by the safety switch 36 is above a specified value (“yes” instep S114), the control part 30 corrects the first threshold (stepS119). Therefore, in detection 1 of dewatering after the first thresholdbeing corrected, whether the washings Q are biased may be detected withhigh accuracy through the corrected first threshold, so that eccentricrotation of the dewatering tank 4 is inhibited early.

By referring to FIG. 23, under a condition that the safety switch 36 isnot started (“no” in step S112), if the accumulated value G does notexceed the first threshold (“no” in step S113), the control part 30 doesnot change the correction alternate value which is zero initially (stepS132) and enables the operation to continue (step S133).

On the other hand, under a condition that the safety switch 36 is notstarted (“no” in step S112), when the accumulated value G reaches thefirst threshold and the detect result of detection 1 is NG (“yes” instep S113), the control part 30 sets the count value n at this moment tobe n_(y) and set the accumulated value G at this moment to be G_(y). Thefirst threshold when the count value n is n_(y) is a value acquired bysubtracting the first specified value from n_(y) in the presentembodiment.

The control part 30 determines whether G_(y) is above a value T obtainedby adding the first threshold and a third specified value together (stepS135). The third specified value is a positive value. Under a conditionthat G_(y) is less than T (“no” in step S135), since there substantiallyexists no time deviation between the moment at which the eccentricrotation is detected by detection 1 and the moment at which theeccentric rotation is detected by the safety switch 36, the firstthreshold is determined to be proper. Therefore, the control part 30does not change the first threshold and enables the operation tocontinue (step S136).

Under a condition that G_(y) is above T (“yes” in step S135), it can bedetermined that there exists a time deviation between the moment atwhich the eccentric rotation is detected by detection 1 and the momentat which the eccentric rotation is detected by the safety switch 36, andthe moment at which the eccentric rotation is detected by detection 1 ismuch earlier than that at which the eccentric rotation is detected bythe safety switch 36. However, since the deviation might have occurredby accident, the control part 30 enables a correction alternate value Vto be added by 1 temporarily (step S137). Under a condition that thecorrection alternate value V added by 1 is less than a specified upperlimit value (which is 3 herein) (“no” in step S138), the control part 30does not change the first threshold and enables the operation tocontinue (step S139).

On the other hand, under a condition that the correction alternate valueV added by 1 reaches the specified upper limit value (“yes” in stepS138), the first threshold is not proper because there apparently existsa time deviation between the moment at which the eccentric rotation isdetected by detection 1 and the moment at which the eccentric rotationis detected by the safety switch 36. Therefore, the control part 30 setsa value obtained by adding the first threshold and the third specifiedvalue together to be a new first threshold, thereby changing the firstthreshold and enabling the first threshold to be widened (step S140).Next, the control part 30 resets the correction alternate value V tozero (step S141) and enables the operation to continue (step S142).

In this way, if the control part 30 determines that the washings Q arebiased before eccentric rotation is detected by the safety switch 36(“yes” in step S131), the first threshold is corrected (step S140).Thus, in detection 1 of dewatering after the first threshold beingcorrected, biasing of the washings Q may be detected with high accuracythrough the corrected first threshold, so that eccentric rotation of thedewatering tank 4 is inhibited early. It shall be noted that, themodification 3 may also be combined with modification 1 and modification2.

Next, description is made to a fourth modification. With respect to thesafety switch 36, the following conditions may be imagined: althoughvibration of the dewatering tank 4 is not so large, due to a moving modeof the outer tank 3, the safety switch 36 may be started by lightcontact with the outer tank 3. In order to prevent the dewatering tank 4from stopping rotating caused by error detection of such mechanicalmode, a control action of the fourth modification is carried out inparallel with detection 1. In the control action of the fourthmodification, a threshold, different from the first threshold, is used(which is set to be a fourth threshold). The fourth threshold may alsobe a value same as the first threshold. However, preferably, the fourththreshold is a value lower than the first threshold. In the following,description is made on a premise that the fourth threshold is slightlyless than the first threshold.

FIG. 24 is a flow chart illustrating a control action of the fourthmodification. By referring to FIG. 24, the control part 30 enables thedewatering tank 4 to rotate and starts dewatering (step S151) along withstarting of the dewatering operation. Along with dewatering, detection 1is carried out in the first acceleration stage. At this time, when thesafety switch 36 is switched to “on” (“yes” in step S152), the controlpart 30 sets the accumulated value G at this time to be G_(z) (stepS153).

The control part 30 determines whether G_(z) is above the fourththreshold (step S154). If G_(z) is above the fourth threshold (“yes” instep S154), a result of starting the safety switch 36, i.e., detectioncarried out by the safety switch 36, is normal since the moment at whicheccentric rotation is detected by detection 1 and the moment at whicheccentric rotation is detected by the safety switch 36 are deemed to beconsistent approximately. Therefore, the control part 30 determines thatthe washings Q are biased and causes the dewatering tank 4 to stoprotating (step S155). It shall be noted that, since detection 1 isexecuted simultaneously, the control part 30 may also determine that thewashings Q are biased (step S33 in FIG. 9B) and cause the dewateringtank 4 to stop rotating (step S41 in FIG. 12) when the accumulated valueG becomes above the first threshold (“yes” in step S32 in FIG. 9B), evenif the safety switch 36 is not started (“no” in step S152).

On the other hand, under a condition that G_(z) when the safety switch36 is started is less than the fourth threshold (“no” in step S154), thecontrol part 30 determines that vibration of the dewatering tank 4 isnegligibly small, the safety switch 36 is considered to be subjected tofalse starting and the operation is continued (step S156). Therefore, asuccess rate of the dewatering operation may be improved.

However, when the safety switch 36 is restarted while the operation iscontinuing hereafter, and the starting number of the safety switch 36reach a specified number (which is 3 herein) from the beginning ofdewatering operation (“yes” in step S157), the control part 30determines that the safety switch 36 is started normally and thewashings Q are biased, and causes the dewatering tank 4 to stop rotating(step S155). In other words, until times of eccentric rotation detectedby the safety switch 36 before it is determined that the washings Q arebiased reach the specified number (“no” in step S157), the control part30 suspends rotation stopping of the dewatering tank 4, and theoperation continues. Therefore, rotation stopping of the dewatering tank4 caused by false detection of the mechanical mode of the safety switch36 may be prevented, and eccentric rotation of the dewatering tank 4 isinhibited early. It shall be noted that, the specified number herein isnot limited to 3 and may also be 1. Moreover, preferably, the controlaction of the modification 4 is executed in the first acceleration stagewhere the rotating speed is low to an extent that no problem isgenerated even ignoring starting of the safety switch 36 in step S156.Certainly, the modification 4 may also be combined with modification 1,modification 2 and modification 3.

In addition, a modification 5, as a further modification of themodification 4, may also carry out the control action shown in FIG. 25.In modification 5, steps S153 and S154 in modification 4 are omitted. Inthis case, beginning from dewatering starting (step S151), even if thesafety switch 36 is switched on (“yes” in step S152), the control part30 may also determines that the safety switch 36 is started by mistakeand causes the operation to continue (step S156) if the starting numberof the safety switch 36 do not reach the specified number (which is 3herein) (“no” in step S157). However, as described above, sincedetection 1 is executed simultaneously, the control part 30 may causethe dewatering tank 4 to stop rotating (step S41 in FIG. 12) when theaccumulated value G becomes above the first threshold (“yes” in step S32in FIG. 9B). That is, if the accumulated value G is less than the firstthreshold, the control part 30 may neglect starting of the safety switch36 when the starting number is not greater than 2.

On the other hand, when the starting number of the safety switch 36reach 3 (“yes” in step S157), the control part 30 determines that aresult detected by the safety switch 36 is normal and the washings Q arebiased, thereby enabling the dewatering tank 4 to stop rotating (stepS155). In other words, even in modification 5, like modification 4,until times of eccentric rotation detected by the safety switch 36before it is determined that the washings Q are biased reaches thespecified number (“no” in step S157), the control part 30 suspendsrotation stopping of the dewatering tank 4, and the operation continues.Besides modification 4, modification 5 may also be combined withmodifications 1˜3. However, in modification 4, since false starting ofthe safety switch 36 is determined based on the fourth threshold lessthan the first threshold (referring to FIG. 24), the biasing of thewashings Q may be determined earlier compared with modification 5 so asto cause the dewatering tank 4 to stop rotating.

In the above present embodiment, on the premise that the motor 6 is avariable frequency motor, the motor 6 is controlled based on the dutyratio. However, under a condition that the motor 6 is a brush motor, themotor 6 is controlled based on the voltage applied to the motor 6instead of the duty ratio.

Moreover, in the above description, although specific numerical valuesincluding 120 rpm, 240 rpm, 800 rpm, etc. are used as the rotatingspeed, the specific numerical values are varied according to theperformance of the dewatering machine 1. Moreover, in the abovedescription, in detections 1˜3, the accumulated value G is calculatedbased on the moving average value C_(n). However, if not influenced byerrors, etc, the accumulated value G may also be calculated based on anyinformation value of other information values such as A_(n) and B_(n),which may be reduced as the rotating speed of the motor 6 increases. Inaddition, although the accumulated value G is an accumulated value ofthe moving average values E_(n), the accumulated value G may also be anaccumulated value of difference D_(n) if influences including oppositeposition errors of NS groups do not exist. In addition, in detection 4,although the duty ratio is acquired to perform determination, theacquired duty ratio may be original data of the acquired duty ratios,may also be a correction value corrected as needed and may also be anindex value acquired by transforming the duty ratio just like the movingaccumulated value C_(m).

1. A dewatering machine, comprising: a dewatering tank, formed in acylindrical shape with a central axis extending in a direction inclinedrelative to an up-down direction, wherein the dewatering tank isconfigured to contain washings, and rotate around the central axis so asto dewater the washings; a balancing ring, formed in a hollow annularshape, wherein the balancing ring is coaxially arranged in thedewatering tank, and liquid for achieving rotational balance of thedewatering tank is contained in the balancing ring and flows freely; anda dewatering preparation unit, configured to cause the dewatering tank,in a dewatering preparation stage for the washings, to rotate at arotating speed lower than a lowest rotating speed at which thedewatering tank resonates, so as to detect a biased position of thewashings in the dewatering tank; and cause the dewatering tank to stoprotating immediately before the washings biased in the dewatering tankare positioned, relative to the central axis, at an opposite side of theliquid biased downward in the balancing ring.
 2. A dewatering machine,comprising: a dewatering tank, formed in a cylindrical shape with acentral axis extending in a direction inclined relative to an up-downdirection, wherein the dewatering tank is configured to containwashings, and rotate around the central axis so as to dewater thewashings; an electric motor, configured to cause the dewatering tank torotate; an information value acquisition unit, configured to, when theelectric motor is in an acceleration state of accelerating to a targetrotating speed used for formally dewatering the washings, sequentiallyacquire an information value that should be decreased as a rotatingspeed of the electric motor increases; a counting unit, configured toadd a count value with an initial value of zero by 1 once theinformation value acquisition unit acquires the information value; acalculation unit, configured to calculate an accumulated value of adifference between the information value and a previous informationvalue under a condition that the information value is larger than theprevious information value; a determination unit, configured todetermine that the washings are biased in the dewatering tank under acondition that the accumulated value when the count value is a specifiedvalue reaches a first threshold when the count value is the specifiedvalue; and a stopping unit, configured to cause the dewatering tank tostop rotating when it is determined by the determination unit that thewashings are biased.
 3. The dewatering machine according to claim 2,further comprising an information correction unit, wherein informationcorrection unit is configured to correct the information value throughmoving average before the accumulated value is calculated by thecalculation unit.
 4. The dewatering machine according to claim 2,further comprising an execution unit, wherein the execution unit isconfigured to alternatively execute any of a restarting process and acorrection process under a condition that the dewatering tank is stoppedrotating through the stopping unit, wherein the restarting process is aprocess for restarting to dewater the washings by causing the dewateringtank to rotate again, and the correction process is a process forcorrecting the biasing of the washings in the dewatering tank; and theexecution unit is configured to select to execute the correction processrather than selecting to execute the restarting process in the followingsituation: the restarting process has been executed for a specifiednumber, and the dewatering tank is caused to stop rotating by thestopping unit.
 5. The dewatering machine according to claim 2, furthercomprising an acceleration unit, wherein the acceleration unit causesthe electric motor to accelerate in three stages including a firstacceleration stage, a second acceleration stage and a third accelerationstage, wherein the first acceleration stage refers to an accelerationstage, in which the motor accelerates toward the target rotating speedfrom starting rotating until the rotating speed of the motor reaches afirst rotating speed, wherein the first rotating speed is higher than arotating speed at which the dewatering tank resonates transversely andlower than a rotating speed at which the dewatering tank resonateslongitudinally, the second acceleration stage is an acceleration stage,in which the rotating speed of the motor increases from the firstrotating speed to a second rotating speed higher than the first rotatingspeed, the third acceleration stage is an acceleration stage, in whichthe rotating speed of the motor increases from the second rotating speedto the target rotating speed, the first threshold is independently setin the first acceleration stage, the second acceleration stage and thethird acceleration stage respectively, and the information valueacquisition unit is configured to acquire the information value in thefirst acceleration stage, the second acceleration stage and the thirdacceleration stage respectively, the counting unit causes the countvalue to be added by 1 and calculates the accumulated value, and thedetermination unit determines that the washings are biased in thedewatering tank when the accumulated value reaches the first threshold.6. The dewatering machine according to claim 5, further comprising: aduty ratio acquisition unit, configured to acquire a duty ratio ofvoltage applied to the motor at each specified time in the thirdacceleration stage; and a transformation unit, configured to transformthe duty ratio acquired by the duty ratio acquisition unit into aspecified index value, when the index value reaches a second thresholdfor a corresponding time, the determination unit determines that thewashings are biased in the dewatering tank.
 7. The dewatering machineaccording to claim 6, further comprising a threshold modification unit,wherein the threshold modification unit is configured to modify thesecond threshold according to the accumulated value in at least oneacceleration stage of the first acceleration stage, the secondacceleration stage and the third acceleration stage.
 8. The dewateringmachine according to claim 5, wherein when a variation of theaccumulated value reaches a third threshold, the determination unitdetermines that the washings are biased in the dewatering tank.
 9. Adewatering machine, comprising: a dewatering tank, formed in acylindrical shape with a central axis extending in a direction inclinedrelative to an up-down direction, wherein the dewatering tank isconfigured to contain washings, and rotate around the central axis so asto dewater the washings; an outer tank, configured to contain thedewatering tank; an electric motor, configured to cause the dewateringtank to rotate; a determination unit, configured to determine that thewashings are biased in the dewatering tank when an information value,relevant to a rotation state of the electric motor before a rotatingspeed of the electric motor reaches a target rotating speed used forformally dewatering the washings, reaches a threshold; a detection unit,configured to mechanically detect eccentric rotation of the dewateringtank by contacting the outer tank when the dewatering tank eccentricallyrotates along with biasing of the washings in the dewatering tank andthe outer tank is caused to vibrate; and a stopping unit, configured tocause the dewatering tank to stop rotating in one of the followingsituations: it is determined by the determination unit that the washingsare biased; the eccentric rotation of the dewatering tank is detected bythe detection unit.
 10. (canceled)
 11. The dewatering machine accordingto claim 3, further comprising an execution unit, wherein the executionunit is configured to alternatively execute any of a restarting processand a correction process under a condition that the dewatering tank isstopped rotating through the stopping unit, wherein the restartingprocess is a process for restarting to dewater the washings by causingthe dewatering tank to rotate again, and the correction process is aprocess for correcting the biasing of the washings in the dewateringtank; and the execution unit is configured to select to execute thecorrection process rather than selecting to execute the restartingprocess in the following situation: the restarting process has beenexecuted for a specified number, and the dewatering tank is caused tostop rotating by the stopping unit.
 12. The dewatering machine accordingto claim 3, further comprising an acceleration unit, wherein theacceleration unit causes the electric motor to accelerate in threestages including a first acceleration stage, a second acceleration stageand a third acceleration stage, wherein the first acceleration stagerefers to an acceleration stage, in which the motor accelerates towardthe target rotating speed from starting rotating until the rotatingspeed of the motor reaches a first rotating speed, wherein the firstrotating speed is higher than a rotating speed at which the dewateringtank resonates transversely and lower than a rotating speed at which thedewatering tank resonates longitudinally, the second acceleration stageis an acceleration stage, in which the rotating speed of the motorincreases from the first rotating speed to a second rotating speedhigher than the first rotating speed, the third acceleration stage is anacceleration stage, in which the rotating speed of the motor increasesfrom the second rotating speed to the target rotating speed, the firstthreshold is independently set in the first acceleration stage, thesecond acceleration stage and the third acceleration stage respectively,and the information value acquisition unit is configured to acquire theinformation value in the first acceleration stage, the secondacceleration stage and the third acceleration stage respectively, thecounting unit causes the count value to be added by 1 and calculates theaccumulated value, and the determination unit determines that thewashings are biased in the dewatering tank when the accumulated valuereaches the first threshold.
 13. The dewatering machine according toclaim 4, further comprising an acceleration unit, wherein theacceleration unit causes the electric motor to accelerate in threestages including a first acceleration stage, a second acceleration stageand a third acceleration stage, wherein the first acceleration stagerefers to an acceleration stage, in which the motor accelerates towardthe target rotating speed from starting rotating until the rotatingspeed of the motor reaches a first rotating speed, wherein the firstrotating speed is higher than a rotating speed at which the dewateringtank resonates transversely and lower than a rotating speed at which thedewatering tank resonates longitudinally, the second acceleration stageis an acceleration stage, in which the rotating speed of the motorincreases from the first rotating speed to a second rotating speedhigher than the first rotating speed, the third acceleration stage is anacceleration stage, in which the rotating speed of the motor increasesfrom the second rotating speed to the target rotating speed, the firstthreshold is independently set in the first acceleration stage, thesecond acceleration stage and the third acceleration stage respectively,and the information value acquisition unit is configured to acquire theinformation value in the first acceleration stage, the secondacceleration stage and the third acceleration stage respectively, thecounting unit causes the count value to be added by 1 and calculates theaccumulated value, and the determination unit determines that thewashings are biased in the dewatering tank when the accumulated valuereaches the first threshold.
 14. The dewatering machine according toclaim 6, wherein when a variation of the accumulated value reaches athird threshold, the determination unit determines that the washings arebiased in the dewatering tank.
 15. The dewatering machine according toclaim 7, wherein when a variation of the accumulated value reaches athird threshold, the determination unit determines that the washings arebiased in the dewatering tank.
 16. The dewatering machine according toclaim 9, further comprising a threshold correction unit, configured tocorrect the threshold in one of the following situations: a differencebetween the information value and the threshold is above the specifiedvalue when the eccentric rotation of the dewatering tank is detected bythe detection unit; it is determined by the determination unit that thewashings are biased before the eccentric rotation is detected by thedetection unit.
 17. The dewatering machine according to claim 9, furthercomprising a suspending unit, configured to suspend an operationperformed by the stopping unit for stopping the rotation of thedewatering tank, until a detection number of the detection unit reachesa specified number before it is determined by the determination unitthat the washings are biased.